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HEATING AND VENTILATION 


A WORKING MANUAL OF APPROVED PRACTICE 
IN HEATING AND VENTILATING DWELLING- 
HOUSES AND OTHER BUILDINGS, WITH 
PRACTICAL INSTRUCTION IN 
MECHANICAL DETAILS, OPER¬ 
ATION, AND CARE OF 
MODERN INSTAL¬ 
LATIONS 


Rv CHARLES L. HUBBARD, S.B., M.E. 

h 

CONSULTING ENGINEER ON HEATING, VENTILATING 
LIGHTING, AND POWER 


ILLUSTHA TFO 


* 


AMERICAN TECHNICAL SOCIETY 
CHICAGO 
1921 






COPYRIGHT, 1916 , 1920 , BY 
AMERICAN TECHNICAL SOCIETY 


COPYRIGHTED IN GREAT BRITAIN 
ALL RIGHTS RESERVED 


DEC -1 1920 

©CU601767 


0 


V 







INTRODUCTION 


pROPERLY regulated heat and pure air are such important 
; factors in our lives that satisfactory methods of taking care 
of them should be of interest not only to architects, contractors, 
and builders, but also to every house dweller, whether he be owner 
or not. 

<1 The question of ventilation, particularly in connection with big 
factories, theaters, churches, or other buildings which may hold 
a large number of people, is a matter for most careful considera¬ 
tion. The volume of air required must be calculated; the size 
of the ducts and pipes, the velocity at which the air can safely 
be moved, and the size of the fans and motors which will drive 
the air must all be planned to the last detail. Again, the proper 
system of heating is a problem in itself, involving the consideration 
of several questions of importance — cost of installation and 
maintenance, fuel, quantity, and distribution of heat, exposure 
of the building, purposes to which the building is to be put, etc. 

<11 The author has had many years of experience in the design and 
construction of heating and ventilation plants and is also an 
author of note on subjects in his special field. He gives very 
practical suggestions on principles of ventilation, air distribution, 
heat losses from buildings, furnace heating, direct and indirect 
steam heating, direct and indirect hot-water heating, exhaust 
steam heating, and care and mangement of heating plants. The 
article also contains many valuable tables and practical examples 
with complete solutions which the man in the field will find 
extremely useful. 



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CONTENTS 


PAGE 

Systems of warming. 1 

Furnaces. 1 

Direct steam. 2 

Indirect steam. 3 

Direct-indirect radiators. 4 

Direct hot water. 4 

Indirect hot water. 5 

Exhaust steam. 5 

Forced blast.„. 6 

Electric heating. 6 

Principles of ventilation. 7 

Composition of the atmosphere. 7 

Air required for ventilation. 9 

Force for moving air. 11 

Measurements of velocity. 11 

Air distribution. 12 

Heat loss from buildings. 13 

Causes of heat loss. 13 

Loss through walls and windows. 13 

Loss by air-leakage. 14 

Furnace heating. 19 

Types of furnaces. 20 

Grates. 22 

Firepot. 23 

Combustion chamber. 24 

Radiator. 24 

Heating surface. 25 

Efficiency. 25 

Heating capacity. 20 

Location of furnace .. 27 

Smoke-pipes. 27 

Chimney flues.•. 28 

Cold-air box. 28 

Return duct. 29 

Warm-air pipes. 30 

Registers. 33 






































CONTENTS 


Furnace heating (continued) page 

Combination systems. 33 

Care and management of furnaces. 34 

Steam boilers. 36 

Types. 36 

Tubular boilers. 36 

Sectional boilers. 39 

Horsepower for ventilation. 42 

Direct-steam heating. 42 

Types of radiating surface. 43 

Cast-iron radiators. v 43 

Pipe radiators. 45 

Circulation coils. 45 

Efficiency of radiators. 47 

Location of radiators. 49 

Systems of piping. 49 

One-pipe relief system. 52 

One-pipe circuit system. 54 

Radiator connections. 55 

Expansion of pipes. 56 

Air-valves. 58 

Pipe sizes. 60 

Boiler connections. 67 

Blow-off tank. 68 

Indirect steam heating. 71 

Types of heaters. 72 

Efficiency of heaters. 74 

Stacks and casings. 77 

Dampers. 77 

Warm-air flues. 81 

Cold-air ducts. . . 82 

Vent flues.*. 83 

Registers. 87 

Pipe connections. 89 

Pipe‘sizes. 90 

Direct-indirect radiators. 91 

Care and management of steam-heating boilers. 92 

Hot-water heaters. 94 

Types. 94 








































CONTENTS 


PAGE 

Direct hot-water heating. 97 

Systems of circulation. 98 

Types of radiating surface. 99 

Efficiency of radiators. 100 

Systems of piping. 101 

Overhead distribution... 103 

Expansion tank. 103 

Air-venting. 105 

Pipe connections. 105 

Combination systems. 107 

Valves and fittings. 109 

Air-valves. 109 

Pipe sizes. 110 

Indirect hot-water heating. 113 

Types of radiators.•.114 

Size of stacks. 114 

Flues and casings. 115 

Pipe connections. 115 

Pipe sizes. 116 

Care and management of hot-v/ater heaters. 116 

Forced hot-water circulation. 117 

Systems of piping... .•. 117 

Sizes of mains and branches. 118 

Pumps. 120 

Heaters. 122 

Exhaust-steam heating. 124 

Reducing valves. 126 

Grease extractor... 127 

Back-pressure valve. 128 

Exhaust head. 130 

. Automatic return-pumps. 130 

Return traps.'. 132 

Damper-regulators. 134 

Pipe connections. 135 

Vacuum systems. I ll 

Low-pressure or vacuum systems. 141 

Webster system. 141 

Paul system. 145 








































CONTENTS 

PAGE 

Forced blast. 147 

Exhaust method.'. 147 

Plenum method. 148 

Form of heating surface. 148 

Efficiency of pipe heaters. 152 

Efficiency of cast-iron heaters. 157 

Pipe connections. 157 

Pipe sizes. 159 

Fans. 159 

General proportions. 161 

Theory of centrifugal fans. 163 

Disc or propeller fans. 171 

Capacity of disc fans. 172 

Fan engines. 175 

Area of ducts and flues. 178 

Factory heating. 179 

Double-duct system. 183 

Electric heating. 186 

Electric heat and energy. 186 

Construction of electric heaters. 186 

Calculation of electric heaters. 187 

Connections for electric heaters. 187 

Cost of electric heating. 188 

Temperature regulations. 189 

Diaphragm motors. 192 

Dampers. 192 

Telethermometer. 193 

Humidostat. 193 

Air-filters and air-washers... 194 

Heating and ventilation of various classes of buildings. 195 

School buildings. 196 

Hospitals. 202 

Churches. 201 

Halls. 206 

Theaters. 206 

Office buildings. 207 

Apartment houses. 209 

Greenhouses and conservatories. 209 

Care and management. 211 













































INSTALLATION OK IDEAL 43-INCH SECTIONAL STEAM BOILERS 

Courtesy of American Radiator Company, Chicago 



















HEATING AND VENTILATION 

PART I 


SYSTEMS OF WARMING 

Any system of warming must include, first, the combustion 
of fuel, which may take place in a fireplace, stove, or furnace, or a 
steam, or hot-water boiler; second, a system of transmission, by means 
of which the heat may be carried, with as little loss as possible, to the 
place where it is to be used for warming; and third, a system of dif¬ 
fusion, which will convey the heat to the air in a room, and to its 
walls, floors, etc., in the most economical way. 

Stoves. The simplest and cheapest form of heating is the stove. 
The heat is diffused by radiation and convection directly to the objects 
and air in the room, and no special system of transmission is required. 
The stove is used largely in the country, and is especially adapted 
to the warming of small dwelling-houses and isolated rooms. 

Furnaces. Next in cost of installation and in simplicity of 
operation, is the hot-air furnace. In this method, the air is drawn 
over heated surfaces and then transmitted through pipes, while at 
a high temperature, to the rooms where heat is required. Furnaces 
are used largely for warming dwelling-houses, also churches, halls, 
and schoolhouses of small size. They are more costly than stoves, 
but have certain advantages over that form of heating. They require 
less care, as several rooms may be warmed from a single furnace; 
and, being placed in the basement, more space is available in the 
rooms above, and the dirt and litter connected with the care of a stove 
are largely done away with. They require less care, as only one fire 
is necessary to warm all the rooms in a house of ordinary size. One 
great advantage in the furnace method of warming comes from the 
constant supply of fresh air which is required to bring the heat into 
the rooms. While this is greatly to be desired from a sanitary stand¬ 
point, it calls for the consumption of a larger amount of fuel than 
would otherwise be necessary. This is true because heat is required 
to warm the fresh air from out of doors up to the temperature of the 



2 


HEATING AND VENTILATION 


rooms, in addition to replacing the heat lost by leakage and conduction 
through walls and windows. 

A more even temperature may be maintained with a furnace 
than by the use of stoves, owing to the greater depth and size of the 
fire, which allows it to be more easily controlled. 

When a building is placed in an exposod location, there is often 
difficulty in warming rooms on the north and west sides, or on that 
side toward the prevailing winds. This may be overcome to some ex¬ 
tent by a proper location of the furnace and by the use of extra large 
pipes for conveying the hot air to those rooms requiring special at¬ 
tention. 

Direct Steam. Direct steam, so called, is widely used in all 
classes of buildings, both by itself and in combination with other 
systems. The first cost of installation is greater than for a furnace, 
but the amount of fuel required is less, as no outside air supply is 
necessary. If used for warming hospitals, schoolhouses, or other 
buildings where a generous supply of fresh air is desired, this method 
must be supplemented by some form of ventilating system. 

One of the principal advantages of direct steam is the ability 
to heat all rooms alike, regardless of their location or of the action 
of winds. 

When compared with hot-water heating, it has still another 
desirable feature—which is its freedom from damage by the freezing 
of water in the radiators when closed, which is likely to happen in 
unused rooms during very cold weather in the case of the former 
system. 

On the other hand, the sizes of the radiators must be proportioned 
for warming the rooms in the coldest weather, and unfortunately 
there is no satisfactory method of regulating the amount of heat in 
mild weather, except by shutting off or turning on steam in the radia- 
ators at more or less frequent intervals as may be required, unless one 
of the expensive systems of automatic control is employed. In large 
rooms, a certain amount of regulation can be secured by dividing 
the radiation into two or more parts, so that different combinations 
may be used under varying conditions of outside temperature. If 
two radiators are used, their surface should be proportioned, when 
convenient, in the ratio of 1 to 2, in which case one-tnird, two-thirds,, 
or the whole power of the radiation can be used as desired. 


HEATING AND VENTILATION 


3 


Indirect Steam. This system of heating combines some of the 
advantages of both the furnace and direct steam, but is more costly 
to install than either of these. The amount of fuel required is about 
the same as for furnace heating, because in each case the cool fresh 
air must be warmed up to the temperature of the room, before it can 
become a medium for conveying heat to offset that lost by leakage 
and conduction through walls and windows. 

A system for indirect steam may be so designed that it will supply 
a greater quantity of fresh air than the ordinary form of furnace, in 
which case the cost of fuel will of course be increased in proportion to 
the volume of air supplied. Instead of placing the radiators in the 
rooms, a special form of heater is supported near the basement ceiling 
and encased in either galvanized iron or brick. A cold-air supply 
duct is connected with the space below the heater, and warm air pipes 
are taken from the top and connected with registers in the rooms to 
be heated the same as in the case of furnace heating. 

A separate stack or heater may be provided for each register if 
the rooms are large; but, if small and so located that they may be 
reached by short runs of horizontal pipe, a single heater may serve 
for two or more rooms. 

The advantage of indirect steam over furnace heating comes from 
the fact that the stacks may be placed at or near the bases of the flues 
leading to the different rooms, thus doing away with long, horizontal 
runs of pipe, and counteracting to a considerable extent the effect of 
wind pressure upon exposed rooms. Indirect and direct heating are 
often combined to advantage by using the former for the more import¬ 
ant rooms, where ventilation is desired, and the latter for rooms more 
remote or where heat only is required. 

Another advantage is the large ratio between the radiating sur¬ 
face and grate-area, as compared with a furnace; this results in a large 
volume of air being warmed to a moderate temperature instead of a 
smaller quantity being heated to a much higher temperature, thus 
giving a more agreeable quality to the air and rendering it less dry. 

Indirect steam is adapted to all the buildings mentioned in con¬ 
nection with furnace heating, and may be used to much better advan¬ 
tage in those of large size. This applies especially to cases where 
more than one furnace is necessary; for, with steam heat, a single 
boiler, or a battery of boilers, may be made to supply heat for a build- 


4 


HEATING AND VENTILATION 


ing of any size, or for a group of several buildings, if desired, and is 
much easier to care for than several furnaces widely scattered. 

Direct Indirect Radiators. These radiators are placed in the 
room the same as the ordinary direct type. The construction is such 
that when the sections are in place, small flues are formed between 
them; and air, being admitted through an opening in the outside wall, 
passes upward through them and becomes heated before entering the 
room. A switch damper is placed in the casing at the base of the 
radiator, so that air may be taken from the room itself instead of 
from out of doors, if so desired. Radiators of this kind are not used 
to any great extent, as there is likely to be more or less leakage of cold 
air into the room around the base. If ventilation is required, it is 
better to use the regular form of indirect heater with flue and register, 
if possible. It is sometimes desirable to partially ventilate an isolated 
room where it would be impossible to run a flue, and in cases of this 
kind the direct-indirect form is often useful. 

Direct Hot Water. Hot water is especially adapted to the warm- 
. ing of dwellings and greenhouses, owing to the ease with which the 
temperature can be regulated. When steam is used, the radiators are 
always at practically the same temperature, while with hot water the 
temperature can be varied at will. A system for hot-water heating 
costs more to install than one for steam, as the radiators must be larger 
and the pipes more carefully run. On the other hand, the cost of 
operating is somewhat less, because the water need be carried only at 
a temperature sufficiently high to warm the rooms properly in mild 
weather, while with steam the building is likely to become overheated, 
and more or less heat wasted through open doors and windows. 

A comparison of the relative costs of installing and operating hot¬ 
air, steam, and hot-water systems, is given in Table I. 


TABLE 1 

Relative Cost of heating Systems 



Hot Air 

Steam 

Hot Water 

Relative cost of apparatus 

Relative cost, adding repairs and fuel 
for five years 

9 

13 

15 

29* 

29} 

27 

Relative cost, adding repairs and fuel for 
fifteen years 

81 

63 

52* 












HEATING AND VENTILATION 


5 


One disadvantage in the use of hot water is the danger from 
freezing when radiators are shut off in unused rooms. This makes 
it necessary in very cold weather to have all parts of the system turned 
on sufficiently to produce a circulation, even if very slow. This is 
sometimes accomplished by drilling a very small hole (about | inch) 
in the valve-seat, to that when closed there will still be a very slow 
circulation through the radiator, thus preventing the temperature of 
the water from reaching the freezing point. 

Indirect Hot Water. This is used under the same conditions as 
indirect steam, but more especially in the case of dwellings and hospi¬ 
tals. When applied to other and larger buildings, it is customary to 
force the water through the mains by means of a pump. Larger 
heating stacks and supply pipes are required than for steam; but the 
arrangement and size of air-flues and registers are practically the 
same, although they are sometimes made slightly larger in special cases. 

Exhaust Steam. Exhaust steam is used for heating in connection 
with power plants, as in shops and factories, or in office buildings 
which have their own lighting plants. There are two methods of 
using exhaust steam for heating purposes. One is to carry a back 
pressure of 2 to 5 pounds on the engines, depending upon the length 
and size of the pipe mains; and the other is to use some form of vacuum 
system attached to the returns or air-valves, which tends to reduce 
the back pressure rather than to increase it. 

Where the first method is used and a back pressure carried, either 
the boiler pressure or the cut-off of the engines must be increased, to 
keep the mean effective pressure the same and not reduce the horse¬ 
power delivered. In general it is more economical to utilize the ex¬ 
haust steam for heating. There are instances, however, where the 
relation between the quantities of steam required for heating and for 
power are such—especially if the engines are run condensing—that 
it is better to throw the exhaust away and heat with live steam. 
Where the vacuum method is used, these difficulties are avoided; and 
for this reason that method is coming into quite common use. 
If the condensation from the exhaust steam is returned to the 
boilers, the oil must first be removed; this is usually accomplished by 
passing the steam through some form of grease extractor as it leaves 
the engine. The water of condensation is often passed through a 
separating tank in addition to this, before it is deli /ered to the return 


6 


HEATING AND VENTILATION 


pumps. It is better, however, to remove a portion of the oil before 
the steam enters the heating system; otherwise a coating will be formed 
upon the inner surfaces of the radiators, which will reduce their 
efficiency to some extent. 

Forced Blast. This method of heating, in different forms, is 
used for the warming of factories, schools, churches, theaters, halls— 
in fact, any large building where good ventilation is desired. The 
air for warming is drawn or forced through a heater of special design, 
and discharged by a fan or blower into ducts which lead to registers 
placed in the rooms to be warmed. The heater is usually made up in 
sections, so that steam may be admitted to or shut off from any section 
independently of the others, and the temperature of the air regulated 
in this manner. Sometimes a by-pass damper is attached, so that 
part of the air will pass through the heater and part around or over it; 
in this way the proportions of cold and heated air may be so adjusted 
as to give the desired temperature to the air entering the rooms. These 
forms of regulation are common where a blower is used for warming 
a single room, as in the case of a church or hall; but where several 
rooms are warmed, as in a schoolhouse. it is customary to use the 
main or primary heater at the blower for warming the air to a given 
temperature (somewhat below that which is actually required), and 
to supplement this by placing secondary coils or heaters at the bottoms 
of the flues leading to the different rooms. By means of this arrange¬ 
ment, the temperature of each room can be regulated independently 
of the others. The so-called double-duct system is sometimes employed. 
In this case, two ducts are carried to each register, one supplying hot 
air and the other cold or tempered air; and a damper for mixing these 
in the right proportions is placed in the flue, below the register. 

Electric Heating. Unless electricity can be produced at a very 
low cost, it is not practicable for heating residences or large buildings 
The electric heater, however, has quite a wide field of application a 
heating small offices, bathrooms, electric cars, etc. It is a convenient 
method of warming isolated rooms on cold mornings, in late spring and 
early fall, when the regular heating apparatus of the building is lot in 
operation. It has the advantage of being instantly available,. id the 
amount of heat can be regulated at will. Electric heaters are clean, 
do not vitiate the air, and are easily moved from place to place. 


HEATING AND VENTILATION 


7 


PRINCIPLES OF VENTILATION 

Closely connected with the subject of heating is the problem of 
■maintaining air of a certain standard of purity in the various buildings 
occupied. 

The introduction of pure air can be done properly only in con¬ 
nection with some system of heating; and no system of heating is 
complete without a supply of pure air, depending in amount upon the 
kind of building and the purpose for which it is used. 

Composition of the Atmosphere. Atmospheric air is not a simple 
substance but a mechanical mixture. Oxygen and nitrogen, the 
principal constituents, are present in very nearly the proportion of one 
part of oxygen to four parts of nitrogen by weight. Carbonic acid gas, 
the product of all combustion, exists in the proportion of 3 to 5 parts 
in 10,000 in the open country. Water in the form of vapor, varies 
greatly with the temperature and with the exposure of the air to open 
bodies of water. In addition to the above, there are generally present, 
in variable but exceedingly small quantities, ammonia, sulphuretted 
hydrogen, sulphuric, sulphurous, nitric, and nitrous acids, floating 
organic and inorganic matter, and local impurities. Air also contains 
ozone, which is a peculiarly active form of oxygen; and lately another 
constituent called argon has been discovered. 

Oxygen is the most important element of the air, so far as both 
heating and ventilation are concerned. It is the active element in the 
chemical process of combustion and also in the somewhat similar 
process which takes place in the respiration of human beings. Taken 
into the lungs, it acts upon the excess of carbon in the blood, and pos¬ 
sibly upon other ingredients, forming chemical compounds which are 
thrown off in the act of respiration or breathing. 

Nitrogen. The principal bulk of the atmosphere is nitrogen, 
which exists uniformly diffused with oxygen and carbonic acid gas. 
This element is practically inert in all processes of combustion or 
respiration. It is not affected in composition, either by passing through 
a furnace during combustion or through the lungs in the process of 
respiration. Its action is to render the oxygen less active, and to 
absorb some part of the heat produced by the process of oxidation. 

Carbonic acid gas is of itself only a neutral constituent of the 
atmosphere, like nitrogen; and—contrary to the general impression— 
its presence in moderately large quantities (if uncombined with other 


8 


HEATING AND VENTILATION 


substances) is neither disagreeable nor especially harmful. Its 
presence, however, in air provided for respiration, decreases the readi¬ 
ness with which the carbon of the blood unites with the oxygen of the 
air; arid therefore, when present in sufficient quantity, it may cause 
indirectly, not only serious, but fatal results. The real harm of a 
vitiated atmosphere, however, is caused by the other constituent 
gases and by the minute organisms which are produced in the process 
of respiration. It is known that these other impurities exist in fixed 
proportion to the amount of carbonic acid present in an atmosphere 
vitiated by respiration. Therefore, as the relative proportion of 
carbonic acid can easily be determined by experiment, the fixing of a 
standard limit of the amount in which it may be allowed, also limits the 
amounts of other impurities which are found in combination with it. 

When carbonic acid is present in excess of 10 parts in 10,000 
parts of air, a feeling of weariness and stuffiness,generally accompanied 
by a headache, will be experienced; while with even 8 parts in 10,000 
parts a room would be considered close. For general considerations 
of ventilation, the limit should be placed at 6 to 7 parts in 10,000, thus 
allowing an increase of 2 to 3 parts over that present in outdoor air, 
which may be considered to contain four parts in 10,000 under ordi¬ 
nary conditions. 

Analysis of Air. An accurate qualitative and quantitative 
analysis of air samples can be made only by an experienced chemist. 
There are, however, several approximate methods for determining 
the amount of carbonic acid present, which are sufficiently exact for 
practical purposes. Among these the following is one of the simplest: 

The necessary apparatus consists of six clean, dry, and tightly 
corked bottles, containing respectively 100,200,250,300,350, and 400 
cubic centimeters, a glass tube containing exactly 15 cubic centimeters 
to a given mark, and a bottle of perfectly clear, fresh limewater. The 
bottles should be filled with the air to be examined by means of a hand¬ 
ball syringe. Add to the smallest bottle 15 cubic centimeters of the 
limewater, put in the cork, and shake well. If the limewater has a 
milky appearance, the amount of carbonic acid will be at least 16 
parts in 10,000. If the contents of the bottle remain clear, treat the 
bottle of 200 cubic centimeters in the same manner; a milky appear¬ 
ance or turbidity in this would indicate 12 parts in 10,000. In a 
similar manner, turbidity in the 250 cubic centimeter bottle indicates 


HEATING AND VENTILATION 


9 


10 parts in 10,000; in the 300, 8 parts; in the 350, 7 parts; and in the 
400, less than 6 parts. The ability to conduct more accurate analyses 
can be attained only by special study and a knowledge of chemical 
properties and of methods of investigation. 

Another method similar to the above, makes use of a glass 
cylinder containing a given quantity of limewater and provided with a 
piston. A sample of the air to be tested is drawn into the cylinder by 
an upw r ard movement of the piston. The.cylinder is then thoroughly 
shaken, and if the limewater shows a milky appearance, it indicates 
a certain proportion of carbonic acid in the air. If the limewater 
remains clear, the air is forced out, and another cylinder full drawn in, 
the operation being repeated until the limewater becomes milky. 
The size of the cylinder and the quantity of limewater are so propor¬ 
tioned that a change in color at the first, second, third, etc., cylinder 
full of air indicates different proportions of carbonic acid. This test 
is really the same in principle as the one previously described; but the 
apparatus used is in more convenient form. 

Air Required for Ventilation. The amount of air required to 
maintain any given standard of purity can very easily be determined, 
provided we know the amount of carbonic acid given off in the process 
of respiration. It has been found by experiment that the average 
production of carbonic acid by an adult at rest is about .6 cubic foot 
per hour. If we assume the proportion of this gas as 4 parts in 10,000 
in the external air, and are to allow 6 parts in 10,000 in an occupied 
room, the gain will be 2 parts in 10,000; or, in other words, there will 
2 

be- = .0002 cubic foot of carbonic acid mixed with each cubic 

10,000 

foot of fresh air entering the room. Therefore, if one person gives 
off .6 cubic foot of carbonic acid per hour, it will require .6 -f- .0002 
= 3,000 cubic feet of air per hour per person to keep the air in the 
room at the standard of purity assumed—that is, 6 parts of carbonic 
acid in 10,000 of air. 

Table II has been computed in this manner, and shows the 
amount of air which must be introduced for each person in order to 
maintain various standards of purity. 

While this table gives the theoretical quantities of air required 
For different standards of purity, and may be used as a guide, it will be 
better in actual practice to use quantities which experience has shown 



10 


HEATING AND VENTILATION 


to give good results in different types of buildings. In auditoriums 
where the cubic space per individual is large, and in which the atmos¬ 
phere is thoroughly fresh before the rooms are occupied, and the 
occupancy is of only two or three hours’ duration, the air-supply may 
be reduced somewhat from the figures given below. 

TABLE II 


Quantity of Air Required per Person 


Standard Parts of Carbonic 
Acid in 10,000 of Air 
in Room 

Cubic Feet of Air Required per Person 

Per Minute 

Per Hour 

5 

100 

6,000 

6 

50 

3,000 

7 

33 

2,000 

8 

25 

1,500 

9 

20 

1,200 

10 

16 

1,000 


Table III represents good modern practice and may be used 
with satisfactory results: 


TABLE III 

Air Required for Ventilation of Various Classes of Buildings 


Air-Supply per Occupant fob 

Cubic Feet per 
Minute 

Cubic Feet per 
Hour 

Hospitals 

80 to 100 

4, 800 to 6, 000 

High Schools 

50 

3, 000 

Grammar Schools 

40 

2, 400 

Theaters and Assembly Halls 

25 

1, 500 

Churches 

20 

1,200 


When possible, the air-supply to any given room should be based 
upon the number of occupants. It sometimes happens, however, 
that this information is not available, or the character of the room is 
such that the number of persons occupying it may vary, as in the case 
of public waiting rooms, toilet rooms, etc. In instances of this kind, 
the required air-volume may be based upon the number of changes 
per hour. In using this method, various considerations must be taken 
into account, such as the use of the room and its condition as to crowd¬ 
ing, character of occupants, etc. In general, the following will be 
found satisfactory for average conditions: 



















HEATING AND VENTILATION 


11 


TABLE IV 

Number of Changes of Air Required in Various Rooms 


Use of Room 

Changes of Air per Hour 

Public Waiting Room 

4 to 5 

Public Toilets 

5 “ 6 

Coat and Locker Rooms 

4 “ 5 

Museums 

3 “ 4 

Offices, Public 

4 " 5 

Offices, Private 

3 “ 4 

Public Dining Rooms 

4 “ 5 

Living Rooms 

3 “ 4 

Libraries, Public 

4 “ 5 

Libraries, Private 

3 “ 4 


Force for Moving Air. Air is moved for ventilating purposes in 
two ways: (1) by expansion due to heating; (2) by mechanical means. 
The effect of heat on the air is to increase its volume and therefore 
lessen its density or weight, so that it tends to rise and is replaced, by 
the colder air below. The available force for moving air obtained in 
this way is very small, and is quite likely to be overcome by wind or 
external causes. It will be found in general that the heat used for 
producing velocity in this manner, when transformed into work in 
the steam engine, is greatly in 
excess of that required to pro¬ 
duce the same effect by the use of 
a fan. 

Ventilation by mechanical 
means is performed either by 
pressure or by suction. The for¬ 
mer is used for delivering fresh air 
into a building, and the latter for 
removing the foul air from it. 

By both processes the air is moved 
without change in temperature, 
and the force for moving must be sufficient to overcome the effects 
of wind or changes in outside temperature. Some form of fan is used 
for this purpose. 

Measurements of Velocity. The velocity of air in ventilating 
ducts and flues is measured directly by an instrument called an ane¬ 
mometer. A common form of this instrument is shown in Fig. 1 . It 
consists of a series of flat vanes attached to an axis, and a series of dials. 



Fig. 1. Common Form of Anemometer, for 
Measuring Velocity of Air-Currents. 




















12 


HEATING AND VENTILATION 


The revolution of the axis causes motion of the hands in proportion to 
the velocity of the air, and the result can be read directly from the dials 
for any given period. 

For approximate results the anemometer may be slowly moved 
across the opening in either vertical or horizontal parallel lines, so 
that the readings will be made up of velocities taken from all parts of 
the opening. For more accurate work, the opening should be divided 
into a number of squares by means of small twine, and readings taken 
at the center of each. The mean of these readings will give the 
average velocity of the air through the entire opening. 

AIR DISTRIBUTION 

The location of the air inlet to a room depends upon the size of 
the room and the purpose for which it is used. In the case of living 
rooms in dwelling-houses, the registers are placed either in the floor 
or in the wall near the floor; this brings the warm air in at the coldest 
part of the room and gives an opportunity for warming or drying the 
feet if desired. In the case of schoolrooms, where large volumes of 
warm air at moderate temperatures are required, it is best to discharge 
it through openings in the wall at a height of 7 or 8 feet from the floor; 
this gives a more even distribution, as the warmer air tends to rise and 
hence spreads uniformly under the ceiling; it then gradually displaces 
other air, and the room becomes filled with pure ait- without sensible 
currents or drafts. The cooler air sinks to the bottom of the room, and 
can be taken off through ventilating registers placed near the floor. 
The relative positions of the inlet and outlet are often governed to 
some extent by the building construction; but, if possible, they should 
both be located in the same side of the room. Figs. 2, 3, and 4 show 
common arrangements. 

The vent outlet should always, if possible, be placed in an inside 
wall; otherwise it will become chilled and the air-flow through it will 
become sluggish. In theaters and churches which are closely packed, 
the air should enter at or near the floor, in finely-divided streams; and 
the discharge ventilation should be through openings in the ceiling. 
The reason for this is the large amount of animal heat given off from 
the bodies of the audience; this causes the air to become still further 
heated after entering the room, and the tendency is to rise continuously 


HEATING AND VENTILATION 


13 


from floor to ceiling, thus carrying away all impurities from respiration 
as fast as they are given off. 

All audience halls in which the occupants are closely seated should 
be treated in the same manner, when possible. This, however, can¬ 
not always be done, as the seats are often made removable so that the 



OUTSIDE WALL OUTSIDE WALL OUTSIDE WALL 

Fig. 2. Fig. 3. Fig. 4. 

Diagrams Showing Relative Positions of Air Inlets and Outlets as Commonly Arranged. 


floor can be used for other purposes. In cases of this kind, part of 
the air may be introduced through floor registers placed along the outer 
aisles, and the remainder by means of wall inlets the same as for school¬ 
rooms. The discharge ventilation should be partly through registers 
near the floor, supplemented by ample ceiling vents for use when the 
hall is crowded or the outside temperature high. 

The matter of air-velocities, size of flues, etc., will be taken up 
under the head of “Indirect Heating.” 

HEAT LOSS FROM BUILDINGS 

A British Thermal Unit, or B. T. U., has been defined as the 
amount of heat required to raise the temperature of one pound of 
water one degree F. This measure of heat enters into many of the 
calculatipns involved in the solving of problems in heating and ventila¬ 
tion, and one should familiarize himself with the exact meaning of 
the term. 

Causes of Heat Loss. The heat loss from a building is due to 
the following causes: (1) radiation and conduction of heat through 
walls and windows; (2) leakage of warm air around doors and win¬ 
dows and through the walls themselves; and (3) heat required to warm 
the air for ventilation. 

Loss through Walls and Windows. The loss of heat through 
the walls of a building depends upon the material used in construction 


















14 


HEATING AND VENTILATION 


TABLE V 

Meat Losses in B. T. U. per Square Foot of Surface per Hour- 

Southern Exposure 


Difference between Inside and Out¬ 
side Temperatures 


Material 

10° 

20 ° 

30° 

40 ° 

50 ° 

60 ° 

70° 

80 ° 

00° 

100° 

8-in. Brick Wall. 

5 

9 

13 

18 

22 

27 

31 

36 

40 

45 

12-in. Brick Wall. 

4 

7 

10 

13 

16 

20 

23 

26 

30 

33 

16-in. Brick Wall. 

3S 

5 

8 

10 

13 

16 

19 

22 

24 

?” 

20-in. Brick Wall. 

2 8 

4.5 

7 

9 

11 

14 

16 

18 

20 

23 

24-in. Brick Wall. 

2.5 

4 

6 

8 

10 

12 

14 

16 

18 

20 

28-in. Brick Wall. 

2 

3.5 

5 

n 

9 

9 

11 

13 

14 

16 

18 

32-in. Brick Wall. 

1 .5 

3 

4.5 

6 

8 

10 

11 

13 

15 

16 

Single Window. 

12 

24 

36 

49 

60 

73 

85 

93 

no 

122 

Double Window. 

8 

16 

24 

32 

40 

48 

56 

62 

70 

78 

Single Skylight. 

11 

21 

31 

42 

52 

63 

73 

84 

94 

104 

Double Skylight. 

.7 

14 

20 

28 

35 

42 

48 

56 

62 

70 

1-in. Wooden Door. 

4 

8 

12 

16 

20 

24 

28 

32 

36 

40 

2-in. Wooden Door. 

3 

5 

8 

11 

14 

17 

•20 

23 

25 

28 

2-in. Solid Plaster Partition. 

6 

12 

18 

24 

30 

36 

42 

48 

54 

60 

3-in. Solid Plaster Partition. 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

Concrete Floor on Brick Arch.. .. 

2 

4 

6.5 

9 

11 

13 

15 

18 

20 

22 

Wood Floor on Brick Arch. 

1 .5 

3 

4.5 

6 

7 

9 

10 

12 

13 

15 

Double Wood Floor. 

Walls of Ordinary Wooden 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Dwellings. 

3 

5 

8 

1 10 

13 

16 

19 

22 

24 

27 


For solid stone walls, multiply the figures for brick of the same thickness 
by 1.7. Where rooms have a cold attic above or cellar beneath, multiply the 
heat loss through walls and windows by 1.1. 

Correction for Leakage. The figures given in the above table apply only 
to the most thorough construction. For the average well-built house, the 
results should be increased about 10 per cent; for fairly good construction, 
20 per cent; and for poor construction, 30 per cent. 

Table V applies only to a southern exposure; for other exposures multi¬ 
ply the heat loss given in Table V by the factors given in Table VI. 

of the wall, the thickness, the number of layers, and the difference 
between the inside and outside temperatures. The exact amount of 
heat lost in this way is very difficult to determioe theoretically, hence 
we depend principally on the results of experiments. 

Loss by Air-Leakage. The leakage of air from a room varies 
fromr one to two or more changes of the entire contents per hour, 
depending upon the construction, opening of doors, etc. It is com¬ 
mon practice to allow for one change per hour in well-constructed 
buildings where two walls of the room have an outside exposure. As 
the amount of leakage depends upon the extent of exposed wall and 
window surface, the simplest way of providing for this is to increase 
























































HEATING AND VENTILATION 


15 


TABLE VI 

Factors for Calculating Heat Loss for Other than Southern Exposures 


Exposure 

Factor 

N . 

1 .32 

E. 

1.12 

S . 

1 .0 

w . 

1 .20 

N . E. 

1.22 

N . W. 

1 .26 

S . E. 

1 .06 

S . W. 

1.10 

N., E., S., and W., or total exposure 

1.16 


the total loss through walls and windows by a factor depending upon 
the tightness of the building construction. Authorities differ con¬ 
siderably in the factors given for heat losses, and there are various 
methods for computing the same. The figures given in Table V have 
been used extensively in actual practice, and have been found to give 
good results when used with judgment. The table gives the heat losses 
through different thicknesses of walls, doors, windows, etc., in B. T. 
U., per square foot of surface per hour, for varying differences in inside 
and outside temperatures. 

In computing the heat loss through walls, only those exposed to 
the outside air are considered. 

In order to make the use of the table clear, we shall give a num¬ 
ber of examples illustrating its use: 

Example 1. Assuming an inside temperature of 70°, what, will be the 
heat loss from a room having an exposed wall surface of 200 square feet and a 
glass surface of 50 square feet, when the outside temperature is zero? The 
wall is of brick, 16 inches in thickness, and has a southern exposure; the win¬ 
dows are single; and the construction is of the best, so that no account need 
be taken of leakage 

Wc find from Table V, that the factor for a lG-inch brick wall 
with a difference in temperature of 70° is 19, and that for glass (single 
window) under the same condition is 85; therefore, 

Loss through walls = 200 X 19 = 3,800 

Loss through windows = 50 X 85 = 4,250 

Total loss per hour = 8,050 B.T.U. 

Example 2. A room 15 ft. square and 10 ft. high has two exposed walls, 
one toward the north, and the other toward the west.. There are 4 windows, 
$ech 3 fe$t by 6 feet in size. The two in the north wall are double, while the 















16 


HEATING AND VENTILATION 


other two are single. The walls arc of brick, 20 inches in thickness. With an 
inside temperature of 70°, what will be the heat loss per hour when it is 10° 
below zero? 

Total exposed surface = 15 X 10 X 2 = 300 
Glass surface = 3 X 6X4== 72 

Net wall surface = 228 

Difference between inside and outside temperature 80°. 

Factor for 20-inch brick w all is 18. 

Factor for single window is 93. 

Factor for double window is 62. 

The heat losses are as follows: 

Wall, 228 X 18 = 4,104 

Single windows, 36 X 93 = 3,348 
Double windows, 36 X 62 = 2,232 

9,684 B.T.U. 

As one side is toward the north, and the other toward the west, the 
actual exposure is N. W. Looking in Table VI, we find the correction 
factor for this exposure to be 1.26; therefore the total heat loss is 

9,684 X 1.26 = 12,201.84 B. T. U. 

, < 

. Example 3. A dwelling-house of fair wooden construction measures 
160 ft. around the outside; it has 2 stories, each 8 ft. in height; the windows 
are single, and the glass surface amounts to one-fifth the total exposure; the 
attic and cellar are unwarmed. If 8,000 B. T. U. are utilized from each pound 
of coal burned in the furnace, how many pounds will be required per hour to 
maintain a temperature of 70° when it is 20° above zero outside? 

Total exposure = 160 X 16 = 2,560 

Glass surface = 2,560 -r 5 = 512 

Net wall 

Temperature difference = 70 — 20 
Wall 2,048 X 13 = 26,624 

Glass 512 X 60. = 30,720 


57,344 B.T. U. 

As the building is exposed on all sides, the factor for exposure wdll be 
the average of those for N., E., S., and W., or 

(1.32 + 1.12 + 1.0 + 1.20) -r* 4 = 1 16 
The house has a cold cellar and attic, so w r e must increase the heat loss 


= 50 c 


2,048 

. l.rK 





HEATING AND VENTILATION 


17 


10 per cent for each of the first two conditions, and 20 per cent for the 
last. Making these corrections we have: 

57,344 X 1.16 X 1.10 X 1.10 X 1.20 = 96,338 B.T. U. 

If one pound of coal furnishes 8,000 B. T. U., then 961338 ~ 8,000 = 
12 pounds of coal per hour required to warm the building to 70° 
under the conditions stated. 

Approximate Method . For dwelling-houses of the average con¬ 
struction, the following simple method for calculating the heat loss 
may be used. Multiply the total exposed surface by 45, which will 
give the heat loss in B. T. U. per hour for an inside temperature of 70° 
in zero weather. 

This factor is obtained in the following manner: Assume the glass 
surface to be one-sixth the total exposure, which is an average propor¬ 
tion. Then each square foot of exposed surface consists one-sixth 
of glass and five-sixths of wall, and the heat loss for 70° difference in 
temperature would be as follows: 

Wall 4- X 19 = 15.8 
b 

Glass ~ X 85 = 14.1 
o - 

29.9 

Increasing this 20 per cent for leakage, 16 per cent for exposure, and 
10 per cent for cold ceilings, we have: 

29.9 X 1.20 X 1.16 X 1.10 = 45. 

The loss through floors is considered as being offset by including 
the kitchen walls of a dwelling-house, which are warmed by the range, 
and which would not otherwise be included if computing the size of a 
furnace or boiler for heating. 

If the heat loss is required for outside temperatures other than 
zero, multiply by 50 for 10 degrees below, and by 40 for 10. degrees 
above zero. 

This method is convenient for approximations in the case of 
dwelling-houses; but the more exact method should be used for other 
types of buildings, and in all cases for computing the heating surface 
for separate rooms. When calculating the heat loss from isolated 
rooms, the cold inside walls as well as the outside must he considered. 

The loss through a wall next to a cold attic or other un warmed space 
may in general be taken as about two-thirds that of an outside wall. 



18 


HEATING AND VENTILATION 


Heat Loss by Ventilation. One B. T. U. will raise the tempera¬ 
ture of 1 cubic foot of air 55 degrees at average temperatures and 
pressures, or will raise 55 cubic feet 1 degree, so that the heat required 
for the ventilation of any room can be found by the following formula: 


Cu. ft. of air per hour X Number of degrees rise 

55 


B. T. U. required. 


To compute the heat loss for any given room which is to be 
ventilated, first find the loss through walls and windows, and correct 
for exposure and leakage; then compute the amount required for 
ventilation as above, and take the sum of the two. An inside tem¬ 
perature of 70° is always assumed unless otherwise stated. 

Examples. What quantity of heat will be required to warm 100,000 
cubic feet of air to 70° for ventilating purposes when the outside temperature 
is 10 below zero? 


100,000 X 80 55 = 145,454 B. T. U. 


How many B. T. U. will be required per hour for the ventilation of a 
church seating 500 people, in Zero weather? 

Referring to Table III, we find that the total air required per 
hour is 1,200 X 500 = 600,000 cu. ft.; therefore 600,000 X 70 -r- 55 
= 763.636 B. T. U. 

The factor H s . l i ^e m pe rat_ure ^ appK)ximately u for 60 o, 

00 

1.3 for 70°, and 1.5 for 80°. Assuming a temperature of 70° for the 
entering air, we may multiply the air-volume supplied for ventilation 
by 1.1 for an outside temperature of 10° above 0, by 1.3 for zero, and 
by 1.5 for 10° below zero—which covers the conditions most commonly 
met with in practice. 


EXAMPLES FOR PRACTICE 

1. A room in a grammar school 28 ft. by 32 ft. and 12 feet high is 
to accommodate 50 pupils. The walls are of brick 16 inches in thick¬ 
ness; and there are 6 single windows in the room, each 3 ft. by 6 ft.; 
there are warm rooms above and below; the exposure is S. E. How 
many B. T. U. will be required per hour for warming the room, and 
how many for ventilation, in zero weather, assuming the building to 
be of average construction? 

Ans. 22,056 + for warming; 152,727 + for ventilation. 

2. A stone church seating 400 people has walls 20 inches in 
thickness. It has a wall exposure of 5,000 square feet, a glass expos- 




HEATING AND VENTILATION 


19 


ure (single windows) of GOO square feet, and a roof exposure of 7>000 
square feet; the roof is of 2-inch pine plank, and the factor for heat 
loss may be taken the same as for a 2-inch wooden door. The floor 
is of wood on brick arches, and has an area of 4,000 square feet. The 
building is exposed on all sides, and is of first-class construction. 
What will be the heat required per hour for both warming and ventila¬ 
tion when the outside temperature is 20° above zero? 

Ans. 296,380 for warming; 436,363 + for ventilation. 

3. A dwelling-house of average wooden construction measures 
200 feet around the outside, and has 3 stories, each 9 feet high. 
Compute the heat loss by the approximate method when the tem¬ 
perature is 10° below zero. 

Ans. 270,000 B. T. U. per hour. 

FURNACE HEATING 

In construction, a furnace is a large stove with a combustion 
chamber of ample size over the fire, the whole being inclosed in a 
casing of sheet iron or brick. The bottom of the casing is provided 
with a cold-air inlet, and at the top are pipes which connect with 
registers placed in the various rooms to be heated. Cold, fresh air 
is brought from out of doors through a pipe or duct called the cold-air 
box; this air enters the space between the casing and the furnace near 
the bottom, and, in passing over the hot surfaces of the fire-pot and 
combustion chamber, becomes heated. It then rises through the 
warm-air pipes at the top of the casing, and is discharged through the 
registers into the rooms above. 

As the warm air is taken from the top of the furnace, cold air 
flows in through the cold-air box to take its place. The air for heating 
the rooms does not enter the combustion chamber. 

Fig. 5 shows the general arrangement of a furnace with its con¬ 
necting pipes. The cold-air inlet is seen at the bottom, and the hot-air 
pipes at the top; these are all provided with dampers for shutting off or 
regulating the amount of air flowing through them. The feed or fire 
door is shown at the front, and the ash door beneath it; a water-pan is 
placed inside the casing, and furnishes moisture to the warm air before 
passing into the rooms; water is either poured into the pan through an 
opening in the front, provided for this purpose, or is supplied auto¬ 
matically through a pipe. 


20 


HEATING AND VENTILATION 


The fire is regulated by means of a draft slide in the ash door, and 
& cold-air or regulating damper placed in the smoke-pipe. Clean-out 
doors are placed at different points in the casing for the removal of 



ashes and soot. Furnaces are made either of cast iron, or of wrought- 
iron plates riveted together and provided with brick-lined firepots. 
Types of Furnaces. Furnaces may be divided into two general 







































































HEATING AND VENTILATION 


21 


types know n as direct-draft and indirect-draft. Fig. G shows in section 
a common form of direct-draft furnace; the better class have a radi¬ 
ator, generally placed at the top, through which the gases pass before 
reaching the smoke-pipe. They have but one damper, usually 
combined with a cold-air check. Many of the cheaper direct-draft 



Fig. 6. Section through Direct-Draft Furnace 
Courtesy of Fuller-Warren Company, Milwaukee, Wisconsin. 


furnaces haVe no radiator at all, the gases passing directly into the 
smoke-pipe and carrying away much heat that should be utilized. 

The furnace shown in Fig. 6 is made of cast iron and has'a large 
radiator at the top; the smoke connection is shown at the rear. 

Fig. 7 represents another form of direct-draft furnace. In this 
case the radiator is made of sheet-steel plates riveted together with 
tubular flues passing through it. 

In the ordinary indirect-draft type of furnace (see Fig. 8), the 
gases pass downward through flues to a radiator located near the base. 











22 


HEATING AND VENTILATION 


thence upward through another flue to the smoke-pipe. In addition 
to the damper in the smoke-pipe, a direct-draft damper is required 
to give direct connection with the funnel when coal is first put on, to 
facilitate the escape of gas to the chimney. When the chimney draft 



Fig. 7. Stewart “B” Direct-Draft Furnace with Tubular Steel Radiator. 
Portable Form for Hard or Soft Coal. 

Courtesy of Fuller-Warren Company, Milwaukee, Wisconsin. 


is weak, trouble from gas is more likely to be experienced with fur¬ 
naces of this type than with those having a direct draft. 

Grates. No part of a furnace is of more importance than the 
grates. The plain grate rotating about a center pin was for a long 
time the one most commonly used. These grates were usually pro¬ 
vided with a clinker door for removing any refuse too large to pass 
between the grate bars. The action of such grates tends to leave a 




















HEATING AND VENTILATION 


23 


cone of ashes in the center of the fire causing it to burn more freely 
around the edges. A better form of grate is the revolving triangular 
pattern, which is now used in many of the leading furnaces. It con¬ 
sists of a series of triangular bars having teeth. The bars are con¬ 
nected by gears, and are turned by means of a detachable lever. If 



Pig. 8- Indirect-Draft Type of Furnace. Gases Pass Downward to Radiator at Bottom, 

Thence Upward to Smoke-Pipe. 


properly used, this grate will cut a slice of ashes and clinkers from 
under the entire fire with little, if any loss of unconsumed coal. 

The Firepot. Firepots are generally made of cast iron or of steel 
plate lined with firebrick. The depth ranges from about 12 to 18 
inches. In cast-iron furnaces of the better class, the firepot is made 
very heavy, to insure durability and to render it less likely to become 
red-hot. The firepot is sometimes made in two pieces, to reduce the 










































24 


HEATING AND VENTILATION 


liability to cracking. The heating surface is sometimes increased by 
corrugations, pins, or ribs, 

A firebrick lining is necessary in a wrought-iron or steel furnace 
to protect the thin shell from the intense heat of the fire. Since brick- 
lined fircpots are much less effective than cast-iron in transmitting 
heat, such furnaces depend to a great extent for their efficiency on the 
heating surface in the dome and radiator; and this, as a rule, is much 
greater than in those of cast iron. 

Cast-iron furnaces have the advantage when coal is first put on 
(and the drop flues and radiator are cut out by the direct damper) of 
still giving off heat from the firepot, while in the case of brick linings 
very little heat is given off in this way, and the rooms are likely to 
become somewhat cooled before the fresh coal becomes thoroughly 
ignited. 

Combustion Chamber. The body of the furnace above the fire- 
pot, commonly called the dome or feed section, provides a combustion 
chamber. This chamber should be of sufficient size to permit the 
gases to become thoroughly mixed with the air passing up through the 
fire or entering through openings provided for the purpose in the feed 
door. In a w r ell-designed furnace, this space should be somewhat 
larger than the firepot. 

Radiator. The radiator, so called, with which all furnaces of 
the better class are provided, acts as a sort of reservoir in which the 
gases are kept in contact with the air passing over the furnace until 
they have parted with a considerable portion of their heat. Radiators 
are built of cast iron, of steel plate, or of a combination of the two. 
The former is more durable and can be made with fewer joints, but 
owing to the difficulty of casting radiators of large size, steel plate is 
commonly used for the sides. 

The effectiveness of a radiator depends on its form, its heating 
surface, and the difference between the temperature of the gases and 
the surrounding air. Owing to the accumulation of soot, the bottom 
surface becomes practically worthless after the furnace has been in 
use a short time; surfaces, to be effective, must therefore be self¬ 
cleaning. 

If the radiator is placed near the bottom of the furnace the gases 
are surrounded by air at the lowest temperature, which renders the 
radiator more effective for a given size than if placed near the top and 


HEATING AND VENTILATION 


25 


surrounded by warm air. On the other hand, the cold air has a ten¬ 
dency to condense the gases, and the acids thus formed are likely to 
corrode the iron. 

Heating Surface. The different heating surfaces may be de¬ 
scribed as follows: Firepot surface; surfaces acted upon by direct 
rays of heat from the fire, such as the dome or combustion chamber; 
gas- or smoke-heated surfaces, such as flues or radiators; and ex¬ 
tended surfaces, such as pins or ribs. Surfaces unlike in character 
and location, vary greatly in heating power, so that, in making com¬ 
parisons of different furnaces, we must know the kind, form, and 
location of the heating surfaces, as well as the area. 

In some furnaces having an unusually large amount of surface, 
it will be found on inspection that a large part would soon become 
practically useless from the accumulation of soot. In others a large 
portion of the surface is lined with firebrick, or is so situated that the 
air-currents are not likely to strike it. 

The ratio of grate to heating surface varies somewhat according 
to the size of furnace. It may be taken as 1 to 25 in the smaller sizes, 
and 1 to 15 in the larger. 

Efficiency. One of the first items to be determined in esti¬ 
mating the heating capacity of a furnace, is its efficiency—that is, 
the proportion of the heat in the coal that may be utilized for warming. 
The efficiency depends chiefly on the area of the heating surface as 
compared with the grate, on its character and arrangement, and on 
the rate of combustion. The usual proportions between grate and 
heating surface have been stated. The rate of combustion required 
to maintain a temperature of 70° in the house, depends, of course, 
on the outside temperature. In very cold weather a rate of 4 to 5 
pounds of coal per square foot of grate per hour must be main¬ 
tained. 

One pound of good anthracite coal will give off about 13,000 
B. T. U., and a good furnace should utilize 70 per cent of this heat. 
The efficiency of an ordinary furnace is often much less, sometimes 
as low as 50 per cent. 

In estimating the required size of a first-class furnace with good 
chimney draft, we may safely count upon a maximum combustion 
of 5 pounds of coal per square foot of grate per hour, and may assume 
that 8,000 B. T. U. will be utilized for warming purposes from each 


26 


HEATING AND VENTILATION 


pound burned. This quantity corresponds to an efficiency of 60 
per cent. 

Heating Capacity. Having determined the heat loss from a 
buil< ling by the methods previously given, it is a simple matter to 
compute the size of grate necessary to burn a sufficient quantity of 
coal to furnish the amount of heat required for warming. 

In computing the size of furnace, it is customary to consider the 
whole house as a single room, with four outside walls and a cold attic. 
The heat losses by conduction and leakage are computed, and in¬ 
creased 10 per cent for the cold attic, and 16 per cent for exposure. 
The heat delivered to the various rooms may be considered as being 
made up of two parts— first, that required to warm the outside air 
up to 70° (the temperature of the rooms); and second, the quantity 
which must be added to this to offset the loss by conduction and leak¬ 
age. Air is usually delivered through the registers at a temperature 
of 120°, with zero conditions outside, in the best class of residence 


70 

work; so that—— of the heat given to the entering air may be con- 

120 50 

sidered as making up the first part, mentioned above, leaving 

available for purely heating purposes. From this it is evident that 


the heat supplied to the entering air must be equal to 1 


50 

120 


= 2.4 


times that required to offset the loss by conduction and leakage. 

Example. The loss through the walls and windows of a building is 
found to be SO,000 B. T. U. per hour in zero weather. What will be the size 
of furnace required to maintain an inside temperature of 70 degrees? 


From the above, we have the total heat required, equal to 80,000 
X 2.4 = 192,000 B. T. U. per hour. If we assume that 8,000 B. T. 
U. are utilized per pound of coal, then 192,000 8,000 = 24 pounds 

of coal required per hour; and if 5 pounds can be burned on each 

24 

square foot of grate per hour, then—- = 4.8 square feet required. 

D 

A grate 30 inches in diameter has an area of 4.9 square feet, and is the 
size we should use. 

When the outside temperature is taken as 10° below zero, multi¬ 
ply by 2.6 instead of 2.4; and multiply by 2.8 for 20° below. 

Table VII will be found useful in determining the diameter of 
firepot required. 




HEATING AND VENTILATION 


27 


TABLE VII 
Flrepot Dimensions 


Average Diameter of Grate, in Inches 

Area in Square Feet 

18 

1 .77 

20 

2.18 

22 

2.64 

24 

3.14 

26 

3.69 

28 

4:27 

30 

4.91 

32 

5.58 


EXAMPLES FOR PRACTICE 

1. A brick apartment house is 20 feet wide, and has 4 stories, 

each being 10 feet in height. The house is one of a block, and is 
exposed only at the front and rear. The walls are 16 inches thick, 
and the block is so sheltered that no correction need be made for 
exposure. Single windows make up £ the total exposed surface. 
Figure for cold attic but warm basement. What area of grate surface 
will be required for a furnace to keep the house at a temperature of 
70° when it is 10° below zero outside? Ans. 3.5 square feet. 

2. A house having a furnace with a firepot 30 inches in diameter, 

is not sufficiently warmed, and it is decided to add a second furnace 
to be used in connection with the one already in. The heat loss from 
the building is found by computation to be 133,600 B. T. LT. per hour, 
in zero weather. What diameter of firepot will be required for the 
extra furnace? Ans. 24 inches. 

Location of Furnace. A furnace should be so placed that the 
warm-air pipes will be of nearly the same length. The air travels 
most readily through pipes leading toward the sheltered side of the 
house and to the upper rooms. Therefore pipes leading toward the 
north or west, or to rooms on the first floor, should be favored in 
regard to length and size. The furnace should be placed somewhat 
to the north or west of the center of the house, or toward the points 
of compass from which the prevailing winds blow. 

Smoke=Pipes. Furnace smoke-pipes range in size from about 
6 inches in the smaller sizes to 8 or 9 inches in the larger ones. They 
are generally made of galvanized iron of No. 24 gauge or heavier. 
The pipe should be carried to the chimney as directly as possible, 










28 


HEATING AND VENTILATION 


avoiding bends which increase the’resistance and diminish the draft. 
Where a smoke-pipe passes through a partition, it should be pro¬ 
tected by a soapstone or double-perforated metal collar having a 
diameter at least 8 inches greater than that of the pipe. The top of 
the smoke-pipe should not be placed within 8 inches of unprotected 
beams, nor less than 6 inches under beams protected by asbestos or 
plaster with a metal shield beneath. A collar to make tight con¬ 
nection with the chimney should be riveted to the pipe about 5 inches 
from the end, to prevent the pipe being pushed too far into the flue. 
Where the pipe is of unusual length, it is well to cover it to prevent 
loss of heat and the condensation of smoke. 

Chimney Flues. Chimney flues, if built of brick, should have 
walls 8 inches in thickness, unless terra-cotta linings are used, when 
only 4 inches of brickwork is required. Except in small houses 
where an 8 by 8-inch flue may be used, the nominal size of the smoke 
flue should be at least 8 by 12-inches, to allow for contractions or off¬ 
sets. A clean-out door should be placed at the bottom of the flue, 
for removing ashes and soot. A square flue cannot be reckoned at 
its full area, as the corners are of little value. To avoid down drafts, 
the top of the chimney must be carried above the highest point of the 
roof unless provided with a suitable hood or top. 

Cold=Air Box. The cold-air box should be large enough to 
supply a volume of air sufficient to fill all the hot-air pipes at the same 
time. If the supply is too small, the distribution is sure to be unequal, 
and the cellar*will become overheated from lack of air to carry away 
the heat generated. 

If a box is made too small, or is throttled down so that the volume 
of air entering the furnace is not large enough to fill all the pipes, 
it will be found that those leading to the less exposed side of the 
house or to the upper rooms will take the entire supply, and that 
additional air to supply the deficiency will be drawn down through 
registers in rooms less favorably situated. It is common practice 
to make the area of the cold-air box three-fourths the combined 
area of the hot-air pipes. The inlet should be placed where the 
prevailing cold winds will blow into it; this is commonly on the north 
or west side of the house. If it is placed on the side away from the 
wind, warm air from the furnace is likely to be drawn out through 
the cold-air box. 


HEATING AND VENTILATION 


29 


^ FOR RETURNING 
{ AIR FROM A BOVE 


Whatever may be the location of the entrance to the cold-air 
box, changes in the direction of the wind may take place which will 
bring the inlet on the wrong side of the house. To prevent the 
possibility of such changes affecting the action of the furnace, the 
cold-air box is sometimes extended through the house and left open 
at both ends, with check-dampers arranged to prevent back-drafts. 
These checks should be placed some distance from the entrance, to 
prevent their becoming clogged with snow or sleet. 

The cold-air box is generally made of matched boards; but 
galvanized iron is much better; it costs more than wood, but is well 
worth the extra, expense on account of tightness, which keeps the dust 
and ashes from being drawn into the furnace casing to be discharged 
through the registers into the rooms above. 

The cold-air inlet should be covered with galvanized wire netting 
with a mesh of at least three-eighths of an inch. The frame to which 
it is attached should not 
be smaller than the in¬ 
side dimensions of the 
cold-air box. A door to 
admit air from the cellar 
to the cold-air box is 
generally provided. As 
a rule, air should be 
taken from this source, 
only when the house is 
temporarily unoccupied 
or during high winds. 

Return Duct. In 
some cases it is desirable 
to return air to the fur¬ 
nace from the rooms 
above, to be reheated. Ducts for this purpose arc common in places 
whore the winter temperature is frequently below zero. Return 
ducts when used, should be in addition to the regular cold-air box. 
Fig. 9 shows a common method of making the connection between 
the two. By proper adjustment of the swinging damper, the air can 
be taken either from out of doors or through the register from the 
room above. The return register is often placed in the hallway of 


GOLD air 
/NLET ' 

netting 



Fig 9. 


Common Method of Connecting Return Duct to 
Cold-Air Box. 


























30 


HEATING AND VENTILATION 


a house, so that it will take the cold air which rushes in when the 
door is opened and also that which may leak in around it while 
closed. Check-valves or flaps of light gossamer or woolen cloth 
should be placed between the cold-air box and the registers to pre¬ 
vent back-drafts during winds. 

The return duct should not be used too freely at the expense of 
outdoor air, and its use is not recommended except during the night 
when air is admitted to the sleeping rooms through open windows. 

Warm=Air Pipes. The required size of the warm-air pipe to 
any given room, depends on the heat loss from the room and on the 
volume of warm air required to offset this loss. Each cubic foot of 
air warmed from zero to 120 degrees brings into a room 2.2 B. T. U. 
We have already seen that in zero w r eather, with the air entering the 

50 

registers at 120 degrees, only of the heat contained in the air is 

available for offsetting the losses by radiation and conduction, so that 
50 

only 2.2 X = .9 B. T. U. in each cubic foot of entering air can 


be utilized for warming purposes. Therefore, if we divide the com¬ 
puted heat loss in B. T. U. from a room, by .9, it will give the number 
of cubic feet of air at 120 degrees necessary to warm the room in zero 
weather. 

As the outside temperature becomes colder, the quantity of heat 
brought in per cubic foot of air increases; but the proportion avail¬ 
able for warming purposes becomes less at nearly the same rate, so 


TABLE VIII 

Warm-Air Pipe Dimensions 


Diameter of Pipe, 

in Inches , 

. Area 

* n Square Inches 

>Area 

in Square Feet 

6 

28 

.196 

7 

38 

.267 

8 

50 

.349 

9 

64 

.442 

10 

79 

.545 

t 11 

95 

.660 

12 

113 

.785 

13 

133 

.922 

14 

154 

1 .07 

15 

177 

1.23 

16 

201 

1.40 












HEATING AND VENTILATION 


31 


that for all practical purposes we may use the figure .9 for all usual 
conditions. In calculating the size of pipe required, we may assume 
maximum velocities of 260 and 380 feet per minute for rooms on the 
first and second floors respectively. Knowing the number of cubic 
feet of air per minute to be delivered, we can divide it by the velocity, 
which will give us the required area of the pipe in square feet. 

Round pipes of tin or galvanized iron are used for this purpose. 
Table VIII will be found useful in determining the required diameters 
of pipe in inches. 

Example. The heat loss from a room on the second floor is 18,000 B. 
T. U. per hour. What diameter of warm-air pipe will be required? 

18,000 -T- .9 = 20,000 = cubic feet of air required per hour. 
20,000 -7- CO = 333 per minute. Assuming a velocity of 380 feet 
per minute, we have 333 -r- 380 = .87 square foot, which is the 
area of pipe required. Preferring to Table VIII, we find this comes 
between a 12-inch and a 13-inch pipe, and the larger size would 
probably be chosen. 

EXAMPLES FOR PRACTICE 

1. A first-floor room has a computed loss of 27,000 B. T. U. 
per hour when it is 10° below zero. The air for warming is to enter 
through two pipes of equal size, and at a temperature of 120 degrees. 
What will be the required diameter of the pipes? 

Ans. 14 inches. 

2. If in the above example the room had been on the second 
floor, and the air was to be delivered through a single pipe, what 
diameter would be required? 

Ans. 16 inches. 

Since long horizontal runs of pipe increase the resistance and 
loss of heat, they should not in general be over 12 or 14 feet in length. 
This applies especially to pipes leading to rooms on the first floor, 
or to those on the cold side of the house. Pipes of excessive length 
should be increased in size because of the added resistance. 

Figs. 10 and 11 show common methods of running the pipes in 
the basement. The first gives the best results, and should be used 
where the basement is of sufficient height to allow it. A damper 
should be placed in each pipe near the furnace, for regulating the flow 
of air to the different rooms, or for shutting it off entirely when desired. 


32 


HEATING AND VENTILATION 


While round pipe risers give the best results, it is not always 
possible to provide a sufficient space for them, and flat or oval pipes 
are substituted. When vertical pipes must be placed in single par¬ 
titions, much better results will be obtained if the studding can be 



Common-Methods of Running Hot-Air Pipes in Basement. Method Shown in Fig. 10 

is Preferable where Feasible. 


made 5 or 6 inches deep instead of 4 as is usually done. Flues should 
never in any case be made less than 3| inches in depth. Each room 
should be heated by a separate pipe. In some cases, however, it is 
allowable to run a single riser to heat two unimportant rooms on an 
upper floor. A clear space of at least \ inch should be left between 
the risers and studs, and the latter should be carefully tinned, and the 


TABLE IX 

Dimensions of Oval Pipes 


Dimension of Pipe 


Area in Square Inches 


6 ovaled to 5 

in. 

27 

7 

44 

44 

4 

44 

31 

7 

44 

44 

31 

44 

29 

7 

It 

44 

6 

44 

38 

8 

t( 

44 

5 

44 

43 

9 

44 

44 

4 

44 

45 

.9 

(< 

44 

6 

44 

57 

"9 

a 

44 

5 

44 

51 

10 

a 

44 

31 

44 

46 

11 

a 

44 

4 

44 

58 

12 

u 

44 

3§ 

44 

55 

10 

u 

44 

6 

44 

67 

11 

41 

44 

5 

44 

67 

14 

44 

44 

4 

44 

76 

15 

44 

44 

31 

44 

73 

12 

44 

44 

6 

44 

85 

12 

44 

44 

5 

44 

75 

19 

44 

44 

4 

44 

96 

20 

44 

44 

31 

44 

100 
































HEATING AND VENTILATION 


33 


space between them on both sides covered with tin, asbestos, or wire 
lath. 

Table IX gives the capacity of oval pipes. A G-inch pipe ovaled 
to 5 means that a 6-inch pipe has been flattened out to a thickness of 
5 inches, and column 2 gives the resulting area. 

Having determined the size of round pipe required, an equiva¬ 
lent oval pipe can be selected from the table to suit the space available. 

Registers. The registers which control the supply of warm 
air to the rooms, generally have a net area equal to two-thirds of their 
gross area. The net area should be from 10 to 20 per cent greater 
than the area of the pipe connected with it. It is common practice 
to use registers having the short dimensions equal to, and the long 
dimensions about one-half greater than, the diameter-of the pipe. 
This would give standard sizes for different diameters of pipe, as 
listed in Table X. 


TABLE X 


Sizes of Registers for Different Sizes of Pipes 


Diameter of Pipe 

Size of Register 

6 in. 

6 X 10 in. 

7 “ 

7 X 10 '* 

8 “ 

8 X 12 “ 

9 “ 

9 X 14 “ 

10 " 

10 X 15 “ 

11 “ 

11 X 16 “ 

12 “ 

12 X 17 “ 

13 “ 

14 X 20 “ 

14 “ 

14 X 22 “ 

15 “ 

15 X 22 “ 

16 “ 

16 X 24 “ 


Combination Systems. A combination system for heating by 
hot air and hot water consists of an ordinary furnace with some form 
of surface for heating water, placed either in contact with the fire or 
suspended above it. Fig. 12 shows a common arrangement where 
part of the heating surface forms a portion of the lining to the firepot 
and the remainder is above the fire. 

Care must be taken to proportion properly the work to be done 
by the air and the water; else one will operate at the expense of the 
other. One square foot of heating surface in contact with the fire is 
capable of supplying from 40 to 50 square feet of radiating surface, 











34 


heating and ventilation 


and one square foot suspended over the fire will supply from 15 to 25 
square feet of radiation. 

The value or efficiency of the heating surface varies so widely in 
different makes that it is best to state the required conditions to the 



Fig. 12. Combination Furnace, for Heating by Both Hot Air and Hot Water. 

manufacturers and have them proportion the surfaces as their experi¬ 
ence has found best for their particular type of furnace. 

Care and Management of Furnaces. The following general 
rules apply to the management of all hard coal furnaces. 

The fire should be thoroughly shaken once or twice daily in cold 
weather. It is well to keep the firepot heaping full at all times. In 




































HEATING AND VENTILATION 


35 


this way a more even temperature may be maintained, less attention is 
required, and no more coal is burned than when the pot is only partly 
filled. In mild weather the mistake is frequently made of carrying a 
thin fire, which requires frequent attention and is likely to die out. 
Instead, to diminish the temperature in the house, keep the firepot 
full and allow ashes to accumulate on the grate (not under it) by shak¬ 
ing less frequently or less vigorously. The ashes will hold the heat 
and render it an easy matter to maintain and control the fire. When 
feeding coal on a low fire, open the drafts and neither rake nor shake 
the fire till the fresh coal becomes ignited. The air supply to the fire 
is of the greatest importance. An insufficient amount results in incom¬ 
plete combustion and a great loss of heat. To secure proper combus¬ 
tion, the fire should be controlled principally by means of the ash-pit 
through the ash-pit door or slide. 

The smoke-pipe damper should be opened only enough to carry 
off the gas or smoke and to give the necessary draft. The openings 
in the feed door act as a check on the fire, and should be kept closed 
during cold weather, except just after firing, when with a good draft 
they may be partly opened to in< rease the air-supply and promote the 
proper combustion of the gases. 

Keep the ash-pit clear to avoid warping or melting the grate. 
The cold-air box should be kept wide open except during winds or 
when the fire is low. At such times it may be partly, but never com¬ 
pletely closed. Too much stress cannot be laid on the importance 
of a sufficient air-supply to the furnace. It costs little if any more 
to maintain a comfortable temperature in the house night and day 
than to allow the rooms to become so cold during the night that the 
fire must be forced in the morning to warm them up to a comfortable 
temperature. 

In case tne warm air fails at times to reach certain rooms, it 
may be forced into them by temporarily closing the registers in other 
rooms. The current once established will generally continue after 
the other registers have been opened. 

It is best to burn as hard coal as the draft will warrant. Egg 
size is better than larger coal, since for a given weight small lumps 
expose more surface and ignite more quickly than larger ones. The 
furnace and smoke-pipe should be thoroughly cleaned once a year. 


36 


HEATING AND VENTILATION 


This should be done just after the fire has been allowed to go out in 
the spring. 

STEAM BOILERS 

Types. The boilers used for heating are the same as have already 
been described for power work. In addition there is the cast-iron 
sectional boiler, used almost exclusively for dwelling-houses. 

Tubular Boilers. Tubular boilers are largely used for heating 
purposes, and are adapted to all classes of buildings except dwelling- 
houses and the special cases mentioned later, for which sectional 
boilers are preferable. A boiler horse-power has been defined as the 
evaporation of 34| pounds of water from and at a temperature of 212 
degrees, and in doing this 33,317 B. T. U. are absorbed, which are 
again given out when the steam is condensed in the radiators. Hence 
to find the boiler H. P. required for warming any given building, we 
have only to compute the heat loss per hour by the methods already 
given, and divide the result by 33,330. It is more common to divide 
by the number 33,000, which gives a slightly larger boiler and is on 
the side of safety. 

The commercial horse-power of a well-designed boiler is based 
upon its heating surface; and for the best economy in heating work, 
it should be so proportioned as to have about 1 square foot heating of 
surface for each 2 pounds of water to be evaporated from and at 212 
degrees F. This gives 34.5 -f- 2 = 17.2 square feet of heating surface 
per horse-power, which is generally taken as 15 in practice. Makers of 
tubular boilers commonly rate them on a basis of 12 square feet of heat¬ 
ing surface per horse-power. This is a safe figure under the conditions 
of power work, where skilled firemen are employed and where more 
care is taken to keep the heating surfaces free from soot and ashes. 
For heating plants, however, it is better to rate the boilers upon 15 
square feet per horse-power as stated above. 

There is some difference of opinion as to the proper method of 
computing the heating surfaoe of tubular boilers. In general, all 
surface is taken which is exposed to the hot gases on one side and to 
the water on the other. A safe rule, and the one by which Table 
XII is computed, is to take § the area of the shell, f of the rear head, 
less the tube area, and the interior surface of all the tubes. 

The required amount of grate area, and the proper ratio of heat- 


HEATING AND VENTILATION 


37 


ing surface to grate area, vary a good deal, depending on the character 
of the fuel and on the chimney draft. By assuming the probable 
rates of combustion and evaporation, we may compute the required 
grate area for any boiler from the formula: 

c H. P. X 34.5 
E x C » 

in which 

S = Total grate area, in square feet; 

E = Pounds of water evaporated per pound of coal; 

C = Pounds of coal burned per square foot of grate per hour. 
Table XI gives the approximate grate area per H. P. for different 
rates of evaporation and combustion as computed' by the above 
equation. 

TABLE XI 

Grate Area per Horse-Power for Different Rates of Evaporation and 

Combustion 


Pounds op Steam per 
Pound of Coal 

Pounds of Coal Burned per Square Foot of Grate per Hour 

8 lb*. 

10 lb*. 

12 lbs. 

Square Feet of Grate Surface per Horse-Power 

10 

.43 

.35 

00 

<N 

9 

48 

.38 

.32 

8 

54 

.43 

.36 

7 

.62 

.49 

41 

6 

.72 

.58 

.48 


For example, with an evaporation of 8 pounds of steam per pound of 
coal, and a combustion of 10 pounds of coal per square foot of grate, .43 of a 
square foot of grate surface per H. P. would be called for. 


The ratio of heating to grate surface in this type of boiler ranges 
from 30 to 40, and therefore allows under ordinary conditions a com¬ 
bustion of from 8 to 10 pounds of coal per square foot of grate. This 
is easily obtained with a good chimney draft and careful firing. The 
larger the boiler, the more important the plant usually, and the greater 
the care bestowed upon it, so that we may generally count on a higher 
rate of combustion and a greater efficiency as the size of the boiler 
increases. Table XII will be found very useful in determining 
the size of boiler required under different conditions. The grate 
area is computed for an evaporation of 8 pounds of water per pound 































38 


HEATING AND VENTILATION 


TABLE XII 


Diameter 
of Sheli. 
in Inches 

Number 
of Tubes 

Diameter 
of Tubes 
in Inches 

Length 
of Tubes 
in Feet 

Horse- 

Power 

Size of 
Grate in- 
Inches 

Size of 

U PTAKE 

in Inches 

Size of 
Smoke- 
pipe in 
Sq. In 

30 

28 

2^ 

6 

8.5 

24 X 36' 

10x14 

140 




7 

9.9 

24 x 36 

10x14 

140 




8 

11.2 

24 x 36 

10 x 14 

140 




9 

12.6 

24 x 42 

10 x 14- 

140 

* 



10 

14.0 

24 x 42 

10 x 14 

140 

36 

34 

V6 

8 

13.6 

30 x 36 

10 x 16 

160 




9 

15.3 

30 x 42 

10 x 18 

180 




10 

16.9 

30 x 42 

10 x 18 

180 




11 

18.6 

30x48 

10 x 20 

200 


• 


12 

20.9 

30 x 48 

10x20 

200 

42 

34 

3 

9 

18.5 

36 x 42 

10 x20 

200 




10 

20.5 

36 x 42 

10 x20 

200 




11 

22.5 

36 x 48 

10 x 25 

250 




12 

24.5 

36 x 48 

10 x25 

250 




13 

26.5 

36 x 48 

10x28 

280 




14 

28.5 

36 x 54 

10x28 

280 

48 

44 

3 

10 

30.4 

42 x 48 

10x28 

280 




11 

33.2 

42 x 48 

10 x28 

280 




12 

35.7 

42 x 54 

10x32 

320 




13 

38.3 

42 x 54 

10x32 

320 




14 

40.8 

42 x 60 

10x36 

360 




15 

43.4 

42 x 60 

10 x36 

360 




16 

45.9 

42 x 60 

10x36 

360 

64 

54 

3 

11 

34.6 

48 x 54 

10x38 

380 




12 

37.7 

48 x 54 

10x38 

380 




13 

40.8 

48 x 54 

10 x38 

380 




14 

43.9 

48x54 

10x38 

380 




15 

47.0 

48 x 60 

10 x40 

400 




16 

50.1 

48 x60 

10x40 

400 


46 

m 

17 

53.0 

48x60 

10x40 

400 

60 

72 

3 

12 

48.4 

54 x 60 

12 x40 

460 




13 

52.4 

54 x 60 

12x40 

460 




14 

56.4 

54 x 60 

12 x 40 

460 




15 

60.4 

54 x 66 

12x42 

500 




16 

64.4 

54 x 66 

12x42 

500 


64 

3 H 

17 

71.4 

54 x 72 

12 x48 

550 




18 

75.6 

54 x 72 

12x48 

550 

66 

90 

3 

14 

70.1 

60 x 66 

12x48 

500 




15 

75.0 

60 x 72 

12 x 52 

620 




16 

80.0 

60 x 72 

12 x62 

620 


78 

3 X 

17 

86.0 

60 x 78 

12x56 

670 




18 

91.1 

60 x78 

12x56 

670 




19 

96.2 

60 x 78 

12x56 

670 


.62 

4 

20 

93.1 

60x78 

12x56 

670 

72 

114 

3 

14 

87.4 

66x72 

12 x 56 

670 




16 

93.6 

66 x 72 

12x56 

670 




16 

99.7 

66 x 78 

12 x62 

740 


98 

3 H 

17 

106.4 

66 x 78 

12x62 

740 




18 

112.6 

66 x 84 

12x66 

790 




19 

118.8 

66 x 84 

12 x66 

790 


72 

4 

20 

107.3 

66 x 84 

12x06 

790 































HEATING AND VENTILATION 


39 


of coal, which corresponds to an efficiency of about 60 per cent, and 
is about the average obtained in practice for heating boilers. 

The areas of uptake and smoke-pipe are figured on a basis of 
1 square foot to 7 square feet of grate surface, and the results given 
in round numbers. In the smaller sizes the relative size of smoke- 
pipe is greater. The rate of combustion runs from 6 pounds in the 
smaller sizes to 11| in the larger. Boilers of the proportions given 
in the table, correspond w r ell with those used in actual practice, and 
may be relied upon to give good results under all ordinary conditions. 

Water-tube boilers are often used for heating purposes, but more 
especially in connection with power plants. The method of com¬ 
puting the required H. P. is the same as for tubular boilers. 

Sectional Boilers. Fig. 13 shows a comnfon form of cast-iron 
boiler. It is made up of slabs or sections, each one of which is con¬ 
nected by nipples with headers at the sides and top. The top header 
acts as a steam drum, and the lower ones act as mud drums; they also 
receive the water of condensation from the radiators. The gases 
from the fire pass backward and forward through flues and are finally 
taken off at the rear of the boiler. 

Another common form of sectional boiler rs shown in Fig. 14. 
It is made up of sections which increase the length like the one just 
described. These boilers have no drum connecting with the sections; 
but instead, each section connects with the adjacent one through 
openings at the top and bottom, as shown. 

The ratio of heating to grate surface in boilers of this type ranges 
from 15 to 25 in the best makes. They are provided with the usual 
attachments, such as pressure-gauge, water-glass, gauge-cocks, and 
safety-valve; a low-pressure damper regulator is furnished for operat¬ 
ing the draft doors, thus keeping the steam pressure practically con¬ 
stant. A pressure of from 1 to 5 pounds is usually carried on these 
boilers, depending upon the outside temperature. The usual setting 
is simply a covering of some kind of non-conducting material like 
plastic magnesia or asbestos, although some forms are enclosed in 
light brickwork. 

In computing the required size, we may proceed in the same 
manner as in the case of a furnace. For the best types of house¬ 
heating boilers, we may assume a combustion of 5 pounds of coal per 
square foot of grate per hour, and an average efficiency of 60 per cent, 


40 


HEATING AND VENTILATION 


which corresponds to 8,000 B. T. U. per pound of coal, available for 
useful work. 

In the case of direct-steam heating, we have only to supply heat 
to offset that lost by radiation and conduction; so that the grate area 
may be found by dividing the computed heat loss per hour by 8,000, 
which gives the number of pounds of coal; and this in turn, divided 
by 5, will give the area of grate required. The most efficient rate of 



combustion will depend somewhat upon the ratio between the grate 
and heating surface. It has been found by experience that about J- 
of a pound of coal per hour for each square foot of heating surface 
gives the best results; so that, by knowing the ratio of heating surface 
to grate area for any make of heater, we can easily compute the most 
efficient rate of combustion, and from it determine the necessary grate 
area. 































































































HEATING AND VENTILATION 


41 



For example, suppose the heat loss from a building to be 480,000 
B. T. U. per hour, and that we wish to use a heater in which the ratio 
of heating surface to grate area is 24. What will be the most efficient 
rate of combustion and 
the required grate area? 

480,000 -r- 8,000 = 60 
pounds of coal per hour, 
and 24 -f- 4 = 6, which is 
the best rate of combus¬ 
tion to employ; there¬ 
fore 60 -f - 6 = 10, the grate 
area required. 

There are many dif¬ 
ferent designs of cast- 
iron boilers for low-pres¬ 
sure steam and hot-water 
heating. In general, 
boilers having a drum 
connected by nipples 
with each section give dryer steam and hold a steadier water¬ 
line than the second form, especially when forced above their 
normal capacity. The steam, in passing through the openings 
between successive sections in order to reach the outlet, is apt to 
carry with it more or Jess water, and to choke the openings, thus 
producing an uneven pressure in different parts of the boiler. 

In the case of hot-water boilers this objection disappears. 

For steam work the opening between the sections should be of good 
size, with an ample steam space above the water-line; and the nozzles 
for the discharge of steam should be located at frequent intervals 


Fig. 14. Ideal Sectional 36-Inch Steam Boiler. 
Courtesy of American Radiator Company. 


EXAMPLES FOR PRACTICE 

1. The heat loss from a building is 240,000 B. T. U. per hour, 

and the ratio of heating to grate area in the heater to be used is 20. 
What will be the required grate area? Ans. 6 sq. ft. 

2. The heat loss from a building is 168,000 B. T. U. per hour, 
and the chimney draft is such that not over 3 pounds of coal per hour 
can be burned per square foot of grate. What ratio of heating to 
grate area will be necessary, and what will be the required grate area? 

Ans. Ratio, 12. Grate area, 7 sq. ft. 


42 


HEATING AND VENTILATION 


Cast-iron sectional boilers are used for dwelling-houses, small 
schoolhouses, churches, etc., where low pressures are carried. They 
are increased in size by adding more slabs or sections. After a certain 
length is reached, the rear sections become less and less efficient, thus 
limiting the size and power. 

Horse=Power for Ventilation. We already know that one 
B. T. U. will raise the temperature of 1 cubic foot of air 55 degrees, 
or it will raise 100 cubic feet of 55 degrees, or T 5 / F of 1 degree; 
therefore, to raise 100 cubic feet 1 degree, it will take 1 -r- or 
B. T. U.; and to raise 100 cubic feet through 100 degrees, it will take 
W 0 ' X 100 B. T. U. In other words, the B. T. U. required to raise 
any given volume of air through any number of degrees in tempera¬ 
ture, is equal to 

Volume of air in cubic ft. X Degrees raised 
55 


. Example. How many B. T. U. are required to raise 100,000 
cubic feet of air 70 degrees? 


100,000 X 70 
55 


127,272 + 


To compute the H. P. required for the ventilation of a building, 
we multiply the total air-supply, in cubic feet per hour, by the number 
of degrees through which it is to be raised, and divide the result by 55. 
This gives the B. T. U. per hour, which, divided by 33,000, will give 
the H. P. required. In using this rule, always take the air-supply in 
cubic feet per hour. 


EXAMPLES FOR PRACTICE 

1. The heat loss from a building is 1,650,000 B. T. U. per hour. 
There is to be an air-supply of 1,500,000 cubic feet per hour, raised 
through 70 degrees. What is the total boiler H. P. required? 

Ans. 108. 

2. A high school has 10 classrooms, each occupied by 50 pupils. 

Air is to be delivered to the rooms at a temperature of 70 degrees. 
What will be the total H. P. required to heat and ventilate the building 
when it is 10 degrees below zero, if the heat loss through walls and 
windows is 1,320,000 B. T. U. per hour? Ans. 106-f. 


DIRECT-STEAM HEATING 

A system of direct-steam heating consists (1) of a furnace and 




HEATING AND VENTILATION 


43 


boiler for the combustion of fuel and the generation of steam; (2) a 
system of pipes for conveying the steam to the radiators and for 
returning the water of condensation to the boiler; and (3) radiators 
or coils placed in the rooms for diffusing the heat. 

Various types of boilers are used, depending upon the size and 
kind of building to be warmed. Some form of cast-iron sectional 
boiler is commonly used for dwelling-houses, while the tubular or 
w T ater-tube boiler is more usually employed in larger buildings. 
Where the boiler is used for heating purposes only, a low steam-pres¬ 
sure of from 2 to 10 pounds is carried, and the condensation flows 
back by gravity to the boiler, which is placed below the lowest radi¬ 
ator. When, for any reason, a higher pres¬ 
sure is required, the steam for the heating 
system is made to pass through a reducing 
valve, and the condensation is returned to 
the boiler by means of a pump or return trap. 

Types of Radiating Surface. The radi¬ 
ation used in direct-steam heating is made 
up of cast-iron radiators of various forms, 
of pipe radiators, and of circulation coils. 

Cast=Iron Radiators. The general form 
of a cast-iron sectional radiator is shown in 
Fig. 15. Radiators of this type are made 
up of sections, the number depending upon 
the amount of heating surface required. 

Fig. 16 shows an intermediate section of a 
radiator of this type. It is simply a loop 
with inlet and outlet at the bottom. The 
end sections are the same, except that they 
have legs, as shown in Fig. 17. These sections are connected at 
the bottom by special nipples, so that steam entering at the end 
fills the bottom of the radiator, and, being lighter than the air, rises 
through the loops and forces the air downward and toward the farther 
end, where it is discharged through an air-valve placed about midway 
of the last section. For one-pipe steam work the supply-leg section 
is constructed with low-drip hub, and for two-pipe steam work, the 
return-leg section is constructed with low-drip hub. 

There are many designs varying in height and width, to 



Fig. 15. Peerless 2-Column 
Cast-Iron Radiator. 
Courtesy of American Radiator 
Company, Chicago. 















44 


HEATING AND VENTILATION 


suit all conditions. The wall pattern shown in Fig; 18 is very con¬ 
venient when it is desired to place the radiator above the floor, as in 

bathrooms, etc.; it is also a con¬ 
venient form to place under the 
windows of halls and churches 
to counteract the effect of cold 
down drafts. It is adapted to 
nearly every place where the or¬ 
dinary direct radiator can be 
used, and may be connected up 
in different ways to meet the va¬ 
rious requirements. 

A low and moderately shallow 
radiator, with ample space for the 
circulation of air between the 
sections, is more efficient than a 
deep radiator with the sections 
closely packed together. One- 
and two-column radiators, so 
called, are preferable to three- 
and four-column, when there is sufficient space to use them. 




Fig. 16. 


Fig. 17. 


Intermediate and End Sections of Radiator 
Shown in Fig. 15. The end sections 
(at right) have legs. 




Fig. 18. Rococo Wall Radiators. 
Courtesy of American Radiator Company, Chicago. 


The standard height of a radiator is 36 or 38 inches, and, if 
possible, it is better not to exceed this. 






























































HEATING AND VENTILATION 


45 


For small radiators, it is better practice to use lower sections and 
increase the length; this makes the radiator slightly more efficient 
and gives a much better appearance. 

To get the best results from wall radiators, they should be set 
out at least \\ inches from the wall to allow a free circulation of air 
back of them. Patterns having cross-bars should be placed, if 
possible, with the bars in a vertical position, as their efficiency is 
impaired somewhat when placed horizontally. 

Pipe Radiators. This type of radiator (see Fig. 19) is made up of 
wrought-iron pipes 
screwed into a cast- 
iron base. The 
pipes are eithercon- 
nected in pairs at 
the top by return 
bends, or each sep¬ 
arate tube has a 
thin metal dia¬ 
phragm passing up 
the center nearly to 
the top. It is nec¬ 
essary that a loop 
be formed, else a 
“dead end” would 
occur. This w T ould 
become filled with 
air and prevent 
steam from enter¬ 
ing, thus causing portions of the radiator to remain cold. 

Circulation Coils. These are usually made up of 1 or 1^-inch 
wrought-iron pipe, and may be hung on the walls of a room by means 
of hook plates, or suspended overhead on hangers and rolls. 

Fig. 20 shows a common form for schoolhouse and similar work; 
this coil is usually made of l|-inch pipe screwed into headers or 
branch tees at the ends, and is hung on the wall just below the windows. 
This is known as a branch coil. Fig. 21 shows a trombone coil, which 
is commonly used when the pipes cannot turn a corner, and where 
the entire coil must be placed upon one side of the room. Fig. 22 



Fig. 19. Wrought-iron Pipe Radiator. 






























46 


HEATING AND VENTILATION 


is called a miter coil, and is used under the same conditions as a trom¬ 
bone coil if there is room for the vertical portion. This form is not 
so pleasing in appearance as either of the other two, and is found only 
in factories or shops, where looks are of minor importance. 



Fig. 20. Common Form of “Branch" Coil for Circulation of Direct Steam. 


Overhead coils are usually of the miter form, laid on the side and 
suspended about a foot from the ceiling; they are less efficient than 
when placed nearer the floor, as the warm air stays at the ceiling and 
the lower part of the room is likely to remain cold. They are used 



Fig. 21. “Trombone" Coil. Used where Entire Coil must be Placed on One Side of Room 

only when wall coils or radiators would be in the way of fixtures, or 
when they would come below the water-line of the boiler if placed 
near the floor. 

When steam is first turned on a coil, it usually passes through a 



portion of the pipes first and heats them while the others remain cold 
and full of air. Therefore the coil must always be made up in such 
a way that each pipe shall have a certain amount of spring and may 
expand independently without bringing undue strains upon the others. 
Circulation coils should incline about 1 inch in 20 feet toward the 










































. HEATING AND VENTILATION 


47 


return end in order to secure proper drainage and quietness of opera¬ 
tion. 

Efficiency of Radiators. The efficiency of a radiator—that is, 
the B. T. U. which it gives off per square foot of surface per hour— 
depends upon the difference in temperature between the steam in the 
radiator and the surrounding air, the velocity of the air over the 
radiator, and the quality of the surface, whether smooth or rough. 
In ordinary low-pressure heating, the first condition is practically 
constant; but the second varies somewhat with the pattern of the 
radiator. An open design which allows the air to circulate freely 
over the radiating surfaces, is more efficient than a closed pattern, 
and for this reason a pipe coil is more efficient than a radiator. 

In a large number of tests of cast-iron and pipe radiators, working 
under usual conditions, the heat given off per square foot of surface 
per hour for each degree difference in temperature between the steam 
and surrounding air was found to average about 1.7 B. T. U. The 
temperature of steam at 3 pounds’ pressure is 220 degrees, and 220—70 
= 150, w’hich may be taken as the average difference between the 
temperature of the steam and the air of the room, in ordinary low- 
pressure work. Taking the above results, we have 150 X 1.7 = 255 
B. T. U. as the efficiency of an average cast-iron or pipe radiator. 
This, for convenient use, may be taken as 250. A circulation coil 
made up of pipes from 1 to 2 inches in diameter, will easily give off 
300 B. T. U. under the same conditions; and a cast-iron wall radiator 
with ample space back of it should have an efficiency equal to that 
of a wall coil. While overhead Coils have a higher efficiency than 
cast-iron radiators, their position near the ceiling reduces their effec¬ 
tiveness, so that in practice the efficiency should not be taken over 
250 B. T. U. per hour at the most. Tabulating the above we have: 


TABLE XIII 

Efficiency of Radiators, Colls, etc. 


Type of Radiatino Surface 

Radiation per Square Foot of Surface 
per Hour 

Cast-Iron Sectional and Pipe Radiators 
Wall Radiators 

Ceiling Coils 

Wall Coils 

250 B.T.U. 

300 f “ 

200 to 250 “ 

300 *' 











48 


HEATING AND VENTILATION 


If the radiator is for warming a room which is to be kept at a 
temperature above or below 70 degrees, or if the steam pressure is 
greater than 3 pounds, the radiating surface may be changed in the 
same proportion as the difference in temperature between the steam 
and the air. 

For example, if a room is to be kept at a temperature of 60°, the 
efficiency of the radiator becomes x£i> X 250 = 267; that is, the 
efficiency varies directly as the difference in temperature between the 
steam and the air of the room. It is not customary to consider this 
unless the steam pressure should be raised to 10 or 15 pounds or the 
temperature of the rooms changed 15 or 20 degrees from the normal. 

From the above it is easy to compute the size of radiator for any 
given room. First compute the heat loss per hour by conduction and 
leakage in the coldest weather; then divide the result by the effi¬ 
ciency of the type of radiator to be used. It is customary to make the 
radiators of such size that they will warm the rooms to 70 degrees in 
the coldest weather. As the low-temperature limit varies a good deal 
in different localities, even in the same State, the lowest temperature 
for which we wish to provide must be settled upon before any calcu¬ 
lations are made. In New England and through the Middle and 
Western States, it is usual to figure on warming a building to 70 
degrees when the outside temperature is from zero to 10 degrees 
below. 

The different makers of radiators publish in their catalogues, 
tables giving the square feet of heating surface for different styles and 
heights, and these can be used in determining the number of sections 
required for all special cases. 

If pipe coils are to be used, it becomes necessary to reduce square 
feet of heating surface to linear feet of pipe; this can be done by means 
of the factors given below. 


Square feet of heating surface X 


3 = linear ft. of 1 -in. pipe 

2.3 = “ “ lj-in. “ 

2 = “ li-in. " 

16= “ “ 2 -in. “ 


The size of radiator is made only sufficient to keep the room 
warm after it is once heated; and no allowance is made for warming 
up; that is, the heat given off by the radiator is just equal to that lost 
through walls and windows. This condition is offset in two ways_ 



HEATING AND VENTILATION 


49 


first, when the room is cold, the difference in temperature between 
the steam and the air of the room is greater, and the radiator is more 
efficient; and second, the radiator is proportioned for the coldest 
weather, so that for a greater part of the time it is larger than neces¬ 
sary 


EXAMPLES FOR PRACTICE 

1. The heat loss from a room is 25,000 B. T. U. per hour in 
the coldest weather. What size of direct radiator will be required? 

Ans. 100 square feet. 

2. A schoolroom is to be warmed with circulation coils of 1£- 

inch pipe. The heat loss is 30,000 B. T. U. per hour. What length 
of pipe will be required? An 3. 230 linear feet. 

Location of Radiators, Radiators should, if possible, be placed 
in the coldest part of the room, as under windows or near outside 
doors. In living rooms it is often desirable to keep the windows free, 
in which case the radiators may be placed at one side. Circulation 
coils are run along the outside walls of a room under the windows. 
Sometimes the position of the radiators is decided by the necessary 
location of the pipe risers, so that a certain amount of judgment must 
be used in each special case as to the best arrangement to suit all 
requirements. 

Systems of Piping. There are three distinct systems of piping, 
known as the two-pipe system, the one-pipe relief system, and the one- 
pipe circuit system, with various modifications of each and combina¬ 
tions of the different systems. 

Fig. 23 shows the arrangement of piping and radiators in the 
two-pipe system. The steam main leads from the top of the boiler, 
and the branches are carried along near the basement ceiling. Risers 
are taken from the supply branches, and carried up to the radiators 
on the different floors; and return pipes are brought down to the 
return mains, which should be placed near the basement floor below 
the water-line of the boiler. Where the building is more than two 
stories high, radiators in similar positions on different floors are con¬ 
nected with the same riser, which may run to the highest floor; and a 
corresponding return drop connecting with each radiator is carried 
down beside the riser to the basement. A system in which the main 
horizontal returns are below the water-line of the boiler is said to 


4 


50 


HEATING AND VENTILATION 


have a wet or sealed return. If the returns are overhead and above the 
water-line, it is called a dry return. Where the steam is exposed to 
extended surfaces of water, as in overhead returns, where the con¬ 
densation partially fills the pipes, there is likely to be cracking or 
water-hammer , due to the sudden condensation of the steam a® ?i 
comes in contact with the cooler water. This is especially noticeable 
when steam is first turned into cold pipes and radiators, and the con¬ 
densation is excessive. When dry returns are used, the pipes should 
be large and have a good pitch toward the boiler. 

In the case of sealed returns, the only contact between the steam 



Fig. 23. Arrangement of Piping and Radiators in "Two-Pipe” System. 


and standing water is in the vertical returns, where the exposed sur¬ 
faces are very small (being equal to the sectional area of the pipes), 
and trouble from water-hammer is practically done away with. Dry 
returns should be given an incline of at least 1 inch in 10 feet, while 
for wet returns 1 inch in 20 or even 40 feet is ample. The ends of all 
steam mains and branches should be dripped into the returns. If the 
return is sealed, the drip maybe directly connected as shown in Fig. 
24; but if it is dry, the connection should be provided with a siphon 
loop as indicated in Fig. 25. The loop becomes filled with water, 
and prevents steam from flowing directly into the return. As the 





































































HEATING AND VENTILATION 


51 


condensation collects in the loop, it overflows into the return pipe and 
is carried away. The return pipes in this case are of course filled with 
steam above the water; but it is steam which has passed through 
the radiators and their return connections, and is therefore at a 
slightly lower pressure; 


Steam Wain 




Water 


RetvLirfi 


ft 

l 


U-r>e 




Fig. 24. Drip from Steam Main Connected Directly 
to Sealed Return. 


so that, if steam were ad¬ 
mitted directly from the 
main, it would tend to 
hold back the water in 
more distant returns and 
cause surging and crack¬ 
ing in the pipes. Some¬ 
times the boiler is at a 
lower level than the basement in which the returns are run, and it then 
becomes necessary to establish a false water-line. This is done by 
making connections as shown in Fig. 26. 

It is readily seen that the return water, in order to reach the 
boiler, must flow through the trap, which raises the water-line or 
seal to the level shown by the dotted line. The balance pipe is to 
equalize the pressure above and below the water in the trap, and 
prevent siphonic action, which would tend to drain the water out of 
the return mains after a flow was once started. 

The balance pipe, when possible, should be 15 or 20 feet in 
length, with a throttle-valve placed near its connection with the 

main. This valve 



should be opened just 
enough to allow the 
steam-pressure to act 
upon the air which oc¬ 
cupies the space above 
the water in the trap; 
but it should not be 
opened sufficiently to 
allow the steam to 
enter in large volume and drive the air out. The success of this 
arrangement depends upon keeping a layer or cushion of cool air 
next to the surface of the water in the trap, and this is easily done 
by following the method here described. 























52 


HEATING AND VENTILATION 


Steam Main 


Ba.1 ance 



Pipe 


False. 


Water-lVrje 


Main 


«U 

l 

Return .. 


£ 


One=Pipe Relief System. In this system of piping, the radiators 
have but a single connection, the steam flowing in and the condensa¬ 
tion draining out through the same pipe. Fig. 27 shows the method 
of running the pipes for this system. The steam main, as before, 
leads from the top of the boiler, and is carried to as high a point as the 
basement ceiling will allow; it then slopes downward with a grade 
of about 1 inch in 10 feet, and makes a circuit of the building or a 
portion of it. 

Risers are taken from the top and carried to the radiators above, 
as in the two-pipe system; but in this case, the condensation flows 
back through the same pipe, and drains into the return main near the 

floor through 
drip connections 
which are made 
at frequent in¬ 
tervals. In a 
two-story build¬ 
ing, the bottom 
of each riser to 
the second floor 
is dripped; and 
in larger build¬ 
ings, it is cus¬ 
tomary to drip 
each riser that 
has more than 
one radiator con¬ 
nected with it. If the radiators are large and at a considerable dis¬ 
tance from the next riser, it is better to make a drip connection for 
each radiator. When the return main is overhead, the risers should 
be dripped through siphon loops; but the ends of the branches 
should make direct connection with the returns. This is the reverse 
of the two-pipe system. In this case the lowest pressure is at the 
ends of the mains, so that steam introduced into the returns at these 
points will cause no trouble in the pipes connecting between these and 
the boiler. 

If no steam is allowed to enter the returns, a vacuum will be 
formed, and there will be no pressure to force the water back to the 


Fig. 26 . 


Connections Made to Establish “False” Water-Line 
when Boiler is below Basement Level. 
























HEATING AND VENTILATION 


53 


boiler. A check-valve should always be placed in the main return 



Pig. 27. Arrangement of Piping and Radiators In “One-Pipe Relief” System. 

near the boiler, to prevent the water from flowing out in case of a 
vacuum being formed suddenly in the pipes. 



Pig. 28. Arrangement of Piping and Radiators In “One-Pipe Circuit” System. 


There is but little difference in the cost of the two systems, as 
larger pipes and valves are required for the single-pipe method 
































































































































54 


HEATING AND VENTILATION 


With radiators of medium size and properly proportioned connections, 
the single-pipe system in preferable, there being but one valve to 
operate and only one-half the number of risers passing through the 
lower rooms. 

One=Pipe Circuit System. In this case, illustrated in Fig. 28, the 
steam main rises to the highest point of the basement, as before; and 
then, with a considerable pitch, makes an entire circuit of the build¬ 
ing, and again connects with the boiler below the water-line. Single 

risers are taken 
from the top; and 
the condensa¬ 
tion drains back 
through the 
same pipes, and 
is carried along 
with the flow of 
steam to the ex¬ 
treme end of the 
main, where it is 
returned to the 
boiler. The 
main is made 
large, and of 
the same size 

throughout its entire length. It must be given a good pitch to insure 
satisfactory results. 

One objection to a single-pipe system is that the steam and return 
water are flowing in opposite directions, and the risers must be made 
of extra large size to prevent, any interference. This is overcome in 
large buildings by carrying a single riser to the attic, large enough 
to supply the entire building; then branching and running “drops’’ 
to the basement. In this system the flow of steam is downward, as 
well as that of water. This method of piping may be used with good 
results in two-pipe systems as well. Care must always be taken that 
no pockets or low points occur in any of the lines of pipe; but if for 
any reason they cannot be av :>ided, they should be carefully drained. 

A modification of this system, adapting it to large buildings, is 
shown in diagram in Fig. 29. The riser shown in this case is one of 


- -T 



r---——«--* 

*- i 

t,-K 




1— 


V 


SipVion 

Connection 


I 


CVieoU Valve 
Connection! 


Sealed Return 


Sealed Return 


Fig. 29. “One-Pipe Circuit” System. Adapted to a Large 

Building. 




























































HEATING AND VENTILATION 


55 


several, the number depending upon the size of the building; and 
may be supplied at either bottom or top as rflost desirable. If steam 
is supplied at the bottom of the riser, as shown in the cut, all of the 
drip connections with the return drop, except the upper one, should 



Fig. 90. “Two-Pipe” Connection of Radia¬ 
tor to Riser and Return 



Fig. 31. “One-Pipe” Connection of Radia¬ 
tor to Basement Main. 


be sealed with either a siphon loop or a check-valve, to prevent the 
steam from short-circuiting and holding back the condensation in the 
returns above. If an overhead supply is used, the arrangement 
should be the reverse; that is, all return connections should be sealed 
except the lowest. 

Sometimes a separate drip is carried down from each set of 
radiators, as shown on the lower story, being connected with the 
main return below the water-line of the 
bo’iler. In case this is done, it is well to 
provide a check-valve in each drip below 
the water-line. 

In buildings of any considerable size, 
it is well to divide the piping system into 
sections by means of valves placed in the 
supply and return branches. 

These are for use in case of a break in 
any part of the system, so that it will be 
necessary to shut off only a small part of 
the heating system during repairs. In tall buildings, it is customary 
to place valves at the top and bottom of each riser, for the same 
purpose. 

Radiator Connections. Figs. 30, 31, and 32 show the common 


corresponding 


mmmma 


•9 










Fig. 32. 4 'One-Pipe' ’ Connection 
of Radiator to Riser. 



























































































































56 


HEATING AND VENTILATION 


methods of making connections between supply pipes and radiators. 
Fig. 30 shows a two-pipe connection with a riser; the return is carried 
down to the main below. Fig. 31 shows a single-pipe connection 
with a basement main; and Fig. 32, a single connection with a riser. 

Care must always be taken to make the horizontal part of the 
piping between the radiator and riser as short as possible, and to give 
it a good pitch toward the riser. There are various ways of making 
these connections, especially suited to different conditions; but the 
examples given serve to show the general principle to be followed. 

Figs. 20, 21, and 22 show the common methods of making steam 
and return connections with circulation coils. The position of the 
air-Valve is shown in each case. 

Expansion of Pipes. Cold steam pipes expand approximately 



Pig. 33. Elevation and Plan of Swivel-Joint to Counteract Effects of Expansion and 

Contraction in Pipes. 

1 inch in each 100 feet in length when low-pressure steam is turned 
into them; so that, in laying out a system of piping, we must arrange 
it in such a manner that there will be sufficient “spring” or “give” to 
the pipes to prevent injurious strains. This is done by means of off¬ 
sets and bends. In the case of larger pipes this simple method will 
not be sufficient, and swivel or slip joints must be used to take up the 
expansion. 

The method of making up a swivel-joint is shown in Fig. 33. 
Any lengthening of the pipe A will be taken up by slight turning or 
Swivel movements at the points B and C. A slip-joint is shown in 






















HEATING AND VENTILATION 


57 


8 



Fig. 34. The part c slides inside the shell d, and is made steam- 
tight by a stuffing-box, as shown. The pipes are connected at the 
flanges A and B. 

When pipes ( i 

pass through 
floors or parti¬ 
tions, the wood¬ 
work should be 
protected by gal- 
vanized-iron 
sleeves having a 

diameter from f to 1 inch greater than the pipe. Fig. 35 shows a 

form of adjustable floor-sleeve 
which may be lengthened or 
shortened to conform to the 
thickness of floor or partition. 
If plain sleeves are used, a 
plate should be placed around 


Fig. 34. 


‘Slip-Joint” Connection to Take Care of Expansion 
and Contraction of Pipes. 




Fig. 35. Adjustable Metal Sleeve for Carrying 
Pipe through Floor or Partition. 


Fig. 36. Floor-Plate Adjusted to Plain 
Sleeve for Carrying Pipe through 
Floor or Partition. 


the pipe where it passes through the floor or partition. These are 



Fig. 37. Angle Valve. 


Fig. 38. Offset Valve. 
Valves for Radiator Connections. 


Fig. 39. Corner Valve. 




made in two parts so that they may be put in place after the pipe is 
hung. A plate of this kind is shown in Fig. 3G. 




















































































58 


HEATING AND VENTILATION 


Valves. The different styles commonly used for radiator con¬ 
nections are shown in Figs. 37,38, and 39, and are known as angle, 
offset, and corner valves, respectively. The first is used when the 
radiator is at the top of a riser or when the connections are like those 
shown in Figs. 30, 31, and 32; the second is used when the connection 



Fig. 40. Indicating Effect of Using Globe Valve on Horizontal Steam Supply 

Pipe or Dry Return. 


between the riser and radiator is above the floor; and the third, when 
the radiator has to be set close in the corner of a room and there is not 
space for the usual connection. 

A globe valve should never be used in a horizontal steam supply 

or dry return. The reason for this is plainly 
shown in Fig. 40. In order for water to flow 
through the valve, it must rise to a height 
shown by the dotted line, which would half 
fill the pipes, and cause serious trouble from 
water-hammer. The gate valve shown in 
Fig. 41 does not have this undesirable fea¬ 
ture, as the opening is on a level with the 
bottom of the pipe. 


Fig. 41. Gate Valve. Fig. 42. Simplest Form of Air*Valve. Operated by Hand. 

Air=Valves. Valves of various kinds are used for freeing the 
radiators from air when steam is turned on. Fig. 42 shows the 
simplest form, which is operated by hand. Fig. 43 is a type of auto¬ 
matic valve, consisting of a shell, which is attached to the radiator. 
B is a small opening which may be closed by the spindle C , which 



























































HEATING AND VENTILATION 


59 


is provided with a conical end. D is a strip composed of a layer of 
iron or steel and one of brass soldered or brazed together. The 
action of the valve is as follows: 
when the radiator is cold and filled 
with air the valve stands as shown 
in the cut. When steam is turned 
on, the air is driven out through 
the opening B. As soon as this 
is expelled and steam strikes the 
strip D, the two prongs spring 
apart owing to the unequal ex¬ 
pansion of the two metals due to 
the heat of the steam. This 
raises the spindle C, and closes 
the opening so that no steam can 
escape. If air should collect in 
the valve, and the metal strip 
become cool, it would contract, 
and the spindle would drop and 
allow the air to escape through B 
as before. E is an adjusting nut. F is a float attached to the spindle, 
and is supposed, in case of a sudden rush 
of water with the air, to rise and close the 
opening; this action, however, is some¬ 
what uncertain, especially if the pressure 
of water continues for some time. 

There are other types of valves acting 
on the same principle. The valve shown 



Fig. 43. Radiator Automatic Air-Valve. 
Operated by Metal Strip Z>, Consisting 
of Two Pieces of Metal of Unequal 
Expansive Power. 




Fig. 44. Section of Jenkins Im¬ 
proved Automatic Air-Valve. 


Fig. 45. Automatic Air-Valve. 
Operated by Expansion of 
Drum C Due to Vaporiza¬ 
tion of Alcohol with 
which it is Partly 
Filled. 


in Fig. 44 is closed by the expansion of a piece of vulcanite instead 
of a metal strip, and has no water float. 



















































60 


HEATING AND VENTILATION 


The valve shown in Fig. 45 acts on a somewhat different prin¬ 
ciple. The float C is made of thin brass, closed at top and bottom, 
and is partially filled with wood alcohol. When steam strikes the 
float, the alcohol is vaporized, and creates a pressure sufficient to 
bulge out the ends slightly, which raises the spindle and closes the 
opening B. 

Fig. 46 shows a form of so-called vacuum valve. It acts in a 
similar manner to those already described, but has in addition a 

ball check which prevents the air from being 
drawn into the radiator, should the steam go 
down and a vacuum be formed. If a partial 
vacuum exists in the boiler and radiators, the 
boiling point, and consequently the tempera¬ 
ture of the steam, are lowered, and less heat is 
given off by the radiators. This method of 
operating a heating plant is sometimes advo¬ 
cated for spring and fall, when little heat is re¬ 
quired, and when steam under pressure would 
overheat the rooms. 

Pipe Sizes. The proportioning of the steam 
pipes in a heating plant is of the greatest im¬ 
portance, and should be carefully worked out 
by methods which experience has proved to be 
correct. There are several ways of doing this; 
but for ordinary conditions, Tables XIV, XV, 
and XVI have given excellent results in actual practice. They 
have been computed from what is known as D’Arcy’s formula, with 
suitable corrections made for actual working conditions. As the 
computations are somewhat complicated, only the results will be given 
here, with full directions for their proper use. 

Table XIV gives the flow of steam in pounds per minute for 
pipes of different diameters and with varying drops in pressure be¬ 
tween the supply and discharge ends of the pipe. These quantities 
are for pipes 100 feet in length; for other lengths the results must be 
corrected by the factors given in Table XVI. As the length of pipe 
increases, friction becomes greater, and the quantity of steam dis¬ 
charged in a given time is diminished. 

Table XIV is computed on the assumption that the drop in 



Fig. 46. Vacuum Valve. 





























HEATING AND VENTILATION 


61 


TABLE XIV 

Flow of Steam in Pipes of Various Sizes, with Various Drops in Pres¬ 
sure between Supply and Discharge Ends 


Calculated for 100-Foot Lengths of Pipe 


fb 

o 
• w 

S fc 

Drop in Pressure (Pounds) 

Q 

M 

y* 

H 

1 

1 X 

2 

3 

4 

5 

1 

.44 

.63 

.78 

91 

1.13 

1.31 

1.66 

1.97 

2.26 

1 Yat 

.81 

1.16 

1.43 

1.66 

2.05 

2.39 

3.02 

3.59 

4.12 

i M 

1.06 

1.89 

2.34 

2.71 

3.36 

3.92 

4.94 

5.88 

6.75 

2 

2.93 

. 4.17 

5.16 

5.99 

7.43 

8.65 

10.9 

13.0 

14.9 

2^ 

5.29 

7.52 

9.32 

10.8 

13.4 

15.6 

19.7 

23.4 

26.9 

3 

8.61 

12.3 

15.2 

17.6 

21.8 

25.4 

32 

31.8 

43.7 

3 X 

12.9 

18.3 

22.6 

26.3 

32.5 

37.9 

47.8 

56.9 

65.3 

4 

18.1 

25.7 

31.8 

36.9 

45.8 

53.3 

67.2 

80.1 

91.9 

5 

32.2 

45.7 

56.6 

65.7 

81.3 

94.7 

120 

142 

163 

6 

51.7 

73.3 

90.9 

106 

131 

152 

192 

229 

262 

7 

76.7 

109 

135 

157 

194 

226 

285 

339 

390 

8 

108 

154 

190 

222 

274 

319 

402 

478 

549 

9 

147 

209 

258 

299 

371 

432 

545 

649 

745 

10 

192 

273 

339 

393 

487 

567 

715 

852 

977 

12 

305 

434 

537 

623 

771 

899 

1,130 

1,350 

1,550 

15 

535 

761 

942 

1,090 

1,350 

1.580 

1,990 

2,370 

2,720 


pressure between the two ends of the pipe equals the initial pressure. 
If the drop in pressure is less than the initial pressure, the actual 
discharge will be slightly greater than the quantities given in the table; 

TABLE XV 

Factors for Calculating Flow of Steam in Pipes under Initial Pres¬ 
sures above Five Pounds 

To be used in connection with Table XIV 


Drop in 
Pressure 
in Pounds 


Initial Pressure (Pounds) 


10 

20 

30 

40 

60 

80 

f 

i 

1 

1.27 

1.49 

1.68 

1 .84 

2 13 

2.38 

1.26 

1 .48 

1.66 

1.83 

2 11 

2.36 

1.24 

1 .46 

1.64 

1.80 

2.08 

2.32 

2 

1 21 

1.41 

1.59 

1.75 

2 02 

2.26 

3 

1 17 

1 37 

1.55 

1.70 

1 .97 

2.20 

4 

1.14 

1 .34 

1.51 

1 .66 

1 ,92 

2.14 

5 

1.12 

1 31 

1 .47 

1.62 

1 87 

2.09 


but this difference will be small for pressures up to 5 pounds, and may 
be neglected, as it is on the side of safety. For higher initial pressures, 
Table XV has been prepared. This is to be used in connection with 
Tabic XIV as follows: First find from Table XIV the quantity of 
steam which will be discharged through the given diameter of pipe 

















































62 


HEATING AND VENTILATION 


TABLE XVI 

Factors for Calculating Flow of Steam in Pipes of Other Lengths 

than 100 Feet 


Feet 

Factor 

Feet 

Factor 

Feet 

Factor 

Feet 

Factor 

10 

3.16 

120 

.91 

275 

.60 

600 

.40 

20 

2.24 

130 

.87 

300 

.57 

650 

.39 

30 

1 .82 

140 

.84 

325 

.55 

700 

.37 

40 

1.58 

150 

.81 

350 

.53 

750 

.36 

50 

1 .41 

160 

.79 

375 

.51 

8.00 

.35 

60 

1.29 

170 

.76 

400 

.50 

850 

.34 

70 

1.20 

180 

.74 

425 

.48 

900 

.33 

80 

1.12 

190 

.72 

450 

.47 

950 

.32 

90 

1 .05 

200 

.70 

475 

.46 

1,000 

.31 

100 

1.00 

225 

.66 

500 

.45 


110 

.95 

250 

.63 

550 

.42 




with the assumed drop in pressure; then look in Table XV for the 
factor corresponding with the assumed drop and the higher initial 
pressure to be used. The quantity given in Table XIV, multiplied 
by this factor, will give the actual capacity of the pipe under the given 
conditions. 

Example —What weight of steam will be discharged through a 3-inch 
pipe 100 feet long, with an initial pressure of 60 pounds and a drop of 2 pounds? 

Looking in Table XIV, we find that a 3-inch pipe will dis¬ 
charge 25.4 pounds of steam per minute with a 2-pound drop. Then 
looking in Table XV, we find the factor corresponding to 60 pounds 
initial pressure and a drop of 2 pounds to be 2.02. Then according 
to the rule given, 25.4 X 2.02 = 51.3 pounds, which is the capacity 
of a 3-inch pipe under the assumed conditions. 

Sometimes the problem will be presented in the following way: 
What size of pipe will be required to deliver 80 pounds of steam a 
distance of 100 feet with an initial pressure of 40 pounds and a drop 
of 3 pounds? 

We have seen that the higher the initial pressure with a given 
drop, the greater will be the quantity of steam discharged; therefore 
a smaller pipe will be required to deliver 80 pounds of steam at 40 
pounds than at 3 pounds initial pressure From Table XV, we find 
that a given pipe will discharge 1.7 times as much steam per minute 
with a pressure of 40 pounds and a drop of 3 pounds, as it would with 
a pressure of 3 pounds, dropping to zero. From this it is evident 
that if we divide 80 by 1.7 and look in Table XIV under “3 pounds 



























HEATING AND VENTILATION 


63 


drop” for the result thus obtained, the size of pipe corresponding will 
be that required. Now, 80 -r 1.7 = 47. The nearest number in the 
table marked “3 pounds drop” is 47.8, which corresponds to a Sc¬ 
inch pipe, which is the size required. 

These conditions will seldom be met with in low-pressure heating, 
but apply more particularly to combination power and heating plants, 
and will be taken up more fully under that head. For lengths of 
pipe other than 100 feet, multiply the quantities given in Table XIV 
by the factors found in Table XVI. 

Example —What weight of steam will be discharged per minute through 
a 3§4 n ch pipe 450 feet long, with a pressure of 5 pounds and a drop of 4 pound? 

Table XIV, which may be used for all pressures below 10 pounds, 
gives for a 3^-inch pipe 100 feet long, a capacity of 18.3 pounds for 
the above conditions. Looking in Table XVI, we find the correction 
factor for 450 feet to be .47. Then 18.3 X -47 = 8.6 pounds, the 
quantity of steam which will be discharged if the pipe is 450 feet 
long. 

Examples involving the use of Tables XIV, XV, and XVI in 
combination, are quite common in practice. The following example 
will show the method of calculation: 

What size of pipe will be required to deliver 90 pounds of steam per 
minute a distance of 800 feet, with an initial pressure of 80 pounds and a drop 
of 5 pounds? 

Table XVI gives the factor for 800 feet as .35, and Table XV, 
that for 80 pounds pressure and 5 pounds drop, as 2.09. Then 
90 

—-—— = 123, which is the equivalent quantity we must look 

. 35 X 2.09 

for in Table XIV. We find that a 4-inch pipe will discharge 91.9 
pounds, and a 5-inch pipe 163 pounds. A 4|-inch pipe is not com¬ 
monly carried in stock, and we should probably use a 5-inch in this 
case, unless it was decided to use a 4-inch and allow a slightly greater 
drop in pressure. In ordinary heating w r ork, with pressures varying 
from 2 to 5 pounds, a drop of } pound in 100 feet has been found to 
give satisfactory results. 

In computing the pipe sizes for a heating system by the above 
methods, it would be a long process to work out the size of each 
branch separately. Accordingly Table XVII has been prepared for 
ready use in low-pressure work. 



64 


HEATING AND VENTILATION 


As most direct heating systems, and especially those in school- 
houses, are made up of both radiators and circulation coils, an effi¬ 
ciency of 300 B. T. U. has been taken for direct radiation of whatever 
variety, no distinction being made between the different kinds. This 
gives a slightly larger pipe than is necessary for cast-iron radiators; 
but it is probably offset by bends in the pipes, and in any case gives a 
slight factor of safety. We find from a steam table that the latent 
heat of steam at 20 pounds above a vacuum (which corresponds to 
5 pounds’gauge-pressure) is 954 + B.T. U.—which means that, for 
every pound of steam condensed in a radiator, 954 B. T. U. are given 
off for warming the air of the room. If a radiator has an efficiency 
of 300 B. T. U., then each square foot of surface will condense 300 — 
954 — .314 pound of steam- per hour; so that we may assume in 
round numbers a condensation of £ of a pound of steam per hour for 
each square foot of direct radiation, when computing the sizes of 
steam pipes in low-pressure heating. Table XVII has been calculated 
on this assumption, and gives the square feet of heating surface 

TABLE XVII 

Heating Surface Supplied by Pipes of Various Sizes 

Length of Pipe, 100 Feet 


Size of Pipe 

• 

Square Feet of Heatino Surface 

1 Pound Drop 

} Pound Drop 

1 

80 

114 

H 

145 

210 

li 

190 

340 

2 

525 

750 

2} 

950 

1,350 

3 

1,550 

2,210 

31 

2,320 

3,290 

4 

3,250 

4,620 

5 

5,800 

8,220 

6 

9,320 

13,200 

7 

13,800 

19,620 

8 

19,440 

27,720 


which different sizes of pipe will supply, with drops in pressure of 
£ and \ pounds in each 100 feet of pipe. The former should be used 
for pressures from 1 to 5 pounds, and the latter may be used for 
pressures over 5 pounds, under ordinary conditions. The sizes of 
long mains and special pipes of large size should be proportioned 
directly from Tables XIV, XV, and XVI. 












HEATING AND VENTILATION 


* 65 

Where the two-pipe system is used and the radiators have sepa¬ 
rate supply and return pipes, the risers or vertical pipes may be taken 
from Table XVII; but if the single-pipe system is used, the risers 
must be increased in size, as the steam and water are flowing in oppo¬ 
site directions and must have plenty of room to pass each other. It 
is customary in this case to base the computation on the velocity of 
the steam in the pipes, rather than on the drop in pressure. Assum¬ 
ing, as before, a condensation of one-third of a pound of steam per 
hour per square foot of radiation, Tables XVIII and XIX have been 
prepared for velocities of 10 and 15 feet per second. The sizes given 
in Table XIX have been found sufficient in most cases; but the larger 
sizes, based on a flow of 10 feet per second, give greater safety and 
should be more generally used. The size of the largest riser should 
usually be limited to 2^ inches in school and dwelling-house work, 
unless it is a special pipe carried up in a concealed position. If the 
length of riser is short between the lowest radiator and the main, a 
higher velocity of 20 feet or more may be allowed through this por¬ 
tion, rather than make the pipe excessively large. 

TABLE XVIII TABLE XIX 


Radiating Surface Supplied by Steam Risers 


10 Feet per Second Velocity 

15 Feet per Second Velocity 

Size of Pipe 

Sq. Feet of Radiation 

Size of Pipe 

Sq. Feet of Radiation 

1 in. 

30 

1 in. 

50 

H “ 

60 

H “ 

90 

n “ 

80 

U “ 

120 

2 “ 

130 

2 “ 

200 

2\ “ 

190 

2\ “ 

290 

3 “ 

290 

3 “ 

340 

3§ “ 

390 

31 “ 

590 


EXAMPLES FOR PRACTICE 

1. How many pounds'of steam will be delivered per minute, 

through a 3^-inch pipe 600 feet long, with an initial pressure of 5 
pounds and a drop of % pound? Ans. 7.32 pounds. 

2. Wh i size pipe will be required to deliver 25.52 pounds 
of steam per minute with an initial pressure of 3 pounds and a drop 
of \ pound, the length of the pipe being 50 feet? Ans. 4-inch. 

3. Compute the size of pipe required to supply 10,000 square 
feet of direct radiation (assume ^ of a pound of steam per square 























66 


HEATING AND VENTILATION 


foot per hour) where the distance to the boiler house is 300 feet, and 
the pressure carried is 10 pounds, allowing a drop in pressure of 
4 pounds. Ans. 5-inch (this is slightly larger than is required, while 
a 4-inch is much too small). 


TABLE XX 

Sizes of Returns for Steam Pipes (in Inches) 


Diameter of Steam Pipe 

Diameter of Dry Return 

Diameter of Sealed Return 

1 

1 

f 

H 

1 

1 

1* 

H 

1 

2 

H 

H 

2i 

2 

H 

3 

21 

2 

31 

2} 

2 

4 

3 

2i 

5 

3 

2i 

6 

3* 

3 

7 

3* 

3 

8 

4 

31 

9 

5 

31 

10 

5 

4 

12 

6 

5 


Returns. The size of return pipes is usually a matter of custom 
and judgment rather than computation. It is a common rule among 
steamfitters to make the returns one size smaller than the corre¬ 
sponding steam pipes. This is a good rule for the smaller sizes, but 
gives a larger return than is necessary for the larger sizes of pipe. 
Table XX gives different sizes of steam pipes with the corresponding 
diameters for dry and sealed returns. 

TABLE XXI 


Pipe Sizes for Radiator Connections 


Square Feet of Radiation 

Steam 

Return 

Two-Pipe 

10 to 30 

30 to 48 

48 to 96 

96 to 150 

} inch 

1 

1* “ 

H “ 

} inch 

i “ 
i 

H “ 

Single-Pipe 

10 to 24 

24 to 60 

60 to 80 

80 to 130 

1 inch 

H “ 

11 “ 

2 “ 

























HEATING AND VENTILATION 


67 



The length of run and number of turns in a return pipe should 
be noted, and any unusual conditions provided for. Where the 
condensation is discharged through a trap into a lower pressure, the 
sizes given may be slightly reduced, especially among the larger 
sizes, depending upon the differences in pressure. 

Radiators are usually tapped for pipe connections as shown in 
Table XXI, and these sizes may be 
used for the connections with the 
mains or risers. 

Boiler Connections. The steam 
main should be connected to the 
rear nozzle, if a tubular boiler is 
used, as the boiling of the water is 
less violent at this point and dryer 
steam will be obtained. The shut¬ 
off valve should be placed in such a position that pockets for the 
accumulation of condensation will be avoided. Fig. 47 shows a good 
position for the valve. 

The size of steam connection may be computed by means of the 
methods already given, if desired. But for convenience the sizes 
given in Table XXII may be used with satisfactory results for the 
short runs between the boilers and main header. 


Fig 47. 


Good Position for Shut-03 
Valve. 


TABLE XXII 

Pipe Sizes from Boiler to Main Header 


Diameter of Boiler 

Size of Steam Pipe 

36 inches 

3 inches 

42 “ 

4 “ 

48 “ 

4 " 

54 “ 

5 “ 

60 “ 

5 “ 

66 “ 

6 “ 

72 “ 

6 “ 


i 


The return connection is made through the blow-off pipe, and 
should be arranged so that the boiler can be blown off without draining 
•the returns. A check-valve should be placed in the main return, and 
a plug-cock in the blow-off pipe. Fig. 48 shows in plan a good 
arrangement for these connections. 





















68 


HEATING AND VENTILATION 


The feed connections, with the exception of that part exposed 
in the smoke-bonnet, are always made of brass in the best class of 
work. The small section referred to should be of extra heavy wrought 



Fig. 48. A Good Arrangement of Return and Blow-Off Connections. 

Iron. The branch to each boiler should be provided with a gate 
or globe valve and a check-valve, the former being placed next to the 
boiler. 

Table XXIII gives suitable sizes for return, blow-off, and feed 
pipes for boilers of different diameters. 


TABLE XXIII 

Sizes for Return, Blow-Off, and Feed Pipes 


Di a meter of Boiler 

Size of Pipe 
for Gravity Return 

Size of Blow-Off 
Pipe 

Size of Feed Pipe 

36 inches 

li inches 

11 inches 

1 inch 

42 “ 

2 

H “ 

1 

48 “ 

2 

ij ‘ 

1 “ 

54 “ 

2 \ “ 

2 “ 

H “ 

eo “ 

2 } “ 

2 

H “ 

66 “ 

3 

2J “ 

U “ 

72 “ 

3 

2$ “ 

n “ 


Blow=Off Tank. Where the blow-off pipe connects with a 
sewer, some means must be provided for cooling the water, or the 
expansion and contraction caused by the hot water flowing through 
the drain-pipes will start the joints and cause leaks. For this reason 
it is customary to pass the water through a blow-off tank. A form 
of wrought-iron tank is shown in Fig. 49. It consists of a receiver 
supported on cast-iron cradles. The tank ordinarily stands nearly 
full of cold water. 

The pipe from the boiler enters above the water-line, and the 
sewer connection leads from near the bottom, as shown. A vapor 
pipe is carried from the top of the tank above the roof of the building. 
When water from the boiler is blown into the tank, cold water from 

















































HEATING AND VENTILATION 


69 


the bottom flows into the sewer, and the steam is carried off through 
the vapor pipe. The equalizing pipe is to prevent any siphon action 
which might draw the water out of the tank after a flow is once started. 
As only a part of the water is blown out of a boiler at one time, the 
blow-off tank can be of a comparatively small size. A tank 24 by 48 
inches should be large enough for boilers up to 48 inches in diameter; 



and one 36 by 72 inches should care for a boiler 72 inches in diameter. 
If smaller quantities of water are blown off at one time, smaller tanks 
can be used. The sizes given above are sufficient for batteries of 2 or 
more boilers, as one boiler can be blown off and the water allowed to 
cool before a second one is blown off. Cast-iron tanks are often 
used in place of wrought-iron, and these may be sunk in the ground 
if desired. 















































Courtesy of American Radiator Company, Chicago. 












HEATING AND VENTILATION 

PART It 


INDIRECT STEAM HEATING 

As already stated, in the indirect method of steam heating, a 
special form of heater is placed beneath the floor, and encased in 
galvanized iron or in brickwork. A cold-air box is connected with 
the space beneath the heater; and warm-air pipes at the top are 
connected with registers in the floors or walls as already described for 
furnaces. A separate heater may be provided for each register if the 
rooms are large, or two or mere registers may be connected with the 
same heater if the horizontal runs of pipe are short. Fig. 50 shows 
a section through a heater arranged for introducing hot air into a 
room through a floor register; and Fig. 51 shows the same type of 
heater connected with a wall register. The cold-air box is seen at 
the bottom of the casing; and the air, in passing through the spaces 
between the sections of the heater, becomes warmed, and rises to the 
rooms above. 

Different forms of indirect heaters are shown in Figs. 52 and 53. 
Several sections con¬ 
nected in a single group 
are called a stack. Some¬ 
times the stacks are en¬ 
cased in brickwork built 
up from the basement 
floor, instead of in gal¬ 
vanized iron as shown in 
the cuts. This method 
of heating provides fresh 
air for ventilation, and for 
this reason is especially 
adapted for schoolhouses, hospitals, churches, etc. As com¬ 
pared with furnace heating, it has the advantage of being less 
affected by outside wind-pressure, as long runs of horizontal pipe 



Fig. 50. Steam Heater Placed under Floor Register 
—Indirect System. 




















72 


HEATING AND VENTILATION 




are avoided and the heaters can be placed near the registers. In a 
large building where several furnaces would be required, a single 

boiler can be 
used, and the 
number of stacks 
increased to suit 
the existing con¬ 
ditions, thus 
making it neces¬ 
sary to run but 
a single fire. An¬ 
other advantage 
is the large ratio 
between the 
heating and 
grate surface as 
compared with a 

furnace; and as a result, a large quantity of air is warmed to a moder¬ 
ate temperature, in place of a smaller quantity heated to a much 
higher temperature. This gives a more agreeable quality to the air. 
Direct and indirect systems are often combined, in the living rooms, 
hallways and corridors, having only direct radiators for warming. 

Types of Heaters. Various forms of indirect radiators are shown 
in Figs. 52, 53, 54, and 56. A hot-water radiator may be used for 
steam; but a steam radiator cannot always be used for hot water, as 


Fig. 51. Steam Heater Connected to Wall Register— 
Indirect System. 

Courtesy of American Radiator Company, Chicago 


Fig. 52. One Form of Indirect Steam or Hot-Water Heatsr. 


it must be especially designed to produce a continuous Sow of water 
through it from top to bottom. Figs. 54 and 55 show the outside 
and the interior construction of a common pattern of indirect radiator 









HEATING AND VENTILATION 


73 


designed especially for steam. The arrows in Fig. 55 indicate the 
path of the steam through the radiator, which is supplied at the right, 
while the return connection is at the left. The air-valve in this case 
should be connected in the end of the last section near the return. 



Fig. 53. Another Form of Indirect Steam or Hot-Water Heater. 


A very efficient form of radiator, and one that is especially adapted 
to the warming of large volumes of air, as in schoolhouse work, is 
shown in Fig. 56, and is known as the School pin radiator. This can 



mmmh 




yVtwivJw^ 


■ill 

I 


Fig. 54. Exterior View of a Common Type of Radiator for Indirect-Steam Heating. 


be used for either steam or hot water, as there is a continuous passage 
downward from the supply connection at the top to the return at the 
bottom. These sections or slabs are made up in stacks after the 



Fig. 55. Interior Mechanism of Radiator Shown in Fig. 54. 


manner shown in Fig. 57, which represents an end view of several 
sections connected together with special nipples. 

A very efficient form of indirect heater may be made up of 
wrought-iron pipe joined together with branch tees and return bends. 














































































































































































































74 


HEATING AND VENTILATION 


A heater like that shown in Fig. 58 is known as a box coil. Its effi¬ 
ciency is increased if the pipes are staggered —that is, if the pipes in 
alternate rows are placed over the spaces between those in the row 
below. 

Efficiency of Heaters. The efficiency of an indirect heater 



Fig. 56. “School Pin” Radiator, Especially Adapted for Warming Large Volumes of 

Air by Either Steam or Hot Wa ter. 


depends upon its form, the difference in temperature between the 
steam and the surrounding air, and the velocity with which the air 
passes over the heater. Under ordinary conditions in dwelling-house 
work, a good form of indirect radiator will give off about 2 B. T. U. 
per square foot per hour for 
each degree difference in tem¬ 
perature between the steam 
and the entering air. Assum¬ 
ing a steam pressure of 2 
pounds and an outside tem¬ 
perature of zero, we should 
have a difference in tempera¬ 
ture of about 220 degrees, 
which, under the conditions 
stated, would give an efficiency 
of 220 X 2 = 440 B. T. U. 
per hour for each square foot 
of radiation. By making a similar computation for 10 degrees be¬ 
low zero, we find the efficiency to be 460. In the same manner we 
may calculate the efficiency for varying conditions of steam pressure 
and outside temperature. In the case of schoolhouses and similar 
buildings where large volumes of air are warmed to a moderate tem- 



Fig. 57. End View of Several “School Pin” 
Radiator Sections Connected Together. 








































HEATING AND VENTILATION 


75 


perature, a somewhat higher efficiency is obtained, owing to the in¬ 
creased velocity of the air over the heaters. Where efficiencies of 440 
and 460 are used for dwellings, we may substitute 600 and 620 for 
schoolhouses. This corresponds approximately to 2.7 B. T. U. per 
square foot per hour for a difference of 1 degree between the air and 
steam. 

The principles involved in indirect steam heating are similar 
to those already described in furnace heating. Part of the heat given 
off by the radiator must be used in warming up the air-supply to the 
temperature of the room, and part for offsetting the loss by conduction 
through walls and windows. The method of computing the heating 
surface required, depends upon the volume of air to be supplied to the 
room. In the case of a schoolroom or hall, where the air quantity 



Fig. 58. “Box Coil," Built Up of Wrought-Iron Pipe, for Indirect-Steam Heating. 


is large as compared with the exposed wall and window surface, we 
should proceed as follows: 

First compute the B. T. U, required for loss by conduction 
through walls and windows; and to this, acid the B. T. U. required 
for the necessary ventilation; and divide the sum by the efficiency 
of the radiators. An example will make this clear. 

Example. How many square feet of indirect radiation will be requirea 
to warm and ventilate a schoolroom in zero weather, where the heat loss by 
conduction through walls and windows is 36,000 B. T. U., and the air-supply 
is 100,000 cubic feet per hour? 

By the methods given under “Heat for Ventilation,” we have 

100,000 _ X 70 ^ 127,272 = B. T. U. required for ventilation. 
o5 

36,000 + 127,272 = 163,272 B. T. U. = Total heat required. 

This in turn divided by 600 (the efficiency of indirect radiators 
under these conditions) gives 272 square feet of surface required. 




























76 


HEATING AND VENTILATION 


In the case of a dwelling-house the conditions are somewhat 
changed, for a room having a comparatively large exposure will have 
perhaps only 2 or 3 occupants, so that, if the small air-quantity neces¬ 
sary in this case were used to convey the required amount of heat 
to the room, it would have to be raised to an excessively high temper¬ 
ature. It has been found by experience that the radiating surface 
necessary for indirect heating is about 50 per cent greater than that 
required for direct heating. So for this work we may compute the 
surface required for direct radiation, and multiply the result by 1.5. 

Buildings like hospitals are in a class between dwellings and 
schoolhouses. The air-supply is based on the number of occupants, 
as in schools, but other conditions conform more nearly to dwelling- 
houses. 

To obtain the radiating surface for buildings of this class, we 
compute the total heat required for warming and ventilation as in 
the case of schoolhouses, and divide the sum by the efficiencies given 
for dwellings—that is, 440 for zero weather, and 460 for 10 degrees 
below. 

Example. A hospital ward requires 50,000 cubic feet of air per hour for 
ventilation; and the heat loss by conduction through walls, etc., is 100,000 
B. T. U. per hour. How many square feet of indirect radiation will be required 
to warm the ward in zero weather? 

50,000 X 70 -j- 55 = 63,636 B. T. U. for ventilation; then, 
63,036 + 100,000 _ 

^ ^^ o# ' | oi|iid«rv ivLt* 


EXAMPLES FOR PRACTICE 

1. A schoolroom having 40 pupils is to be warmed and venti¬ 

lated when it is 10 degrees below zero. If the heat loss by conduction 
is 30,000 B. T. U. per hour, and the air supply is to be 40 cubic feet 
per minute per pupil, how many square feet of indirect radiation will 
be required? Ans. 273. 

2. A contagious ward in a hospital has 10 beds, requiring 6,000 

cubic feet of air each, per hour. The heat loss by conduction in zero 
weather is 80,000 B. T. U. How many square feet of indirect radia¬ 
tion will be required? Ans. 355. 

3. The heat loss from a sitting room is 11,250 B. T. U. per 

hour in zero weather. How many square feet of indirect radiation 
will be required to warm it? Ans. 75. 



HEATING AND VENTILATION 


77 


LAG 



END 

VIEW 



Stacks and Casings. It has already been stated that a group of 
•sections connected together is called a stack, and examples of these 
with their casings are shown in Figs. 50 and 51. The casings are 
usually made of galvanized iron, and are made up in sections by 
means of small bolts so that they may be taken apart in case it is 
necessary to make repairs. Large stacks are often enclosed in brick¬ 
work, the sides consisting of 8-inch walls, and the top being covered 
over with a layer of brick and mortar supported on light wrought-iron 
tee-bars. Blocks of asbestos are sometimes used for covering, instead 
of brick, the whole being covered over with plastic material of the 
same kind. 

Where a single stack supplies several flues or registers, the 
connections between these and the warm-air chamber are made in 
the same manner as already described for furnace heating. When 
galvanized-iron casings are used, the heater is supported by hangers 
from the floor above. Fig. 

59 shows the method of 
hanging a heater from a SCRe: ^ / ^ 
wooden floor. If the floor heater 

is of fireproof construc¬ 
tion, the hangers may pass ■ *!_ l ' (d) 

up through the brick- Fig . 59 . 
work, and the ends be 
provided with nuts and large washers or plates; or they may be clamped 
to the iron beams which carry the floor. Where brick casings are 
used, the heaters are supported upon pieces of pipe or light I-beams 
built into the walls. 

The warm-air space above the heater should never be less than 
8 inches, while 12 inches is preferable for heaters of large size. The 
cold-air space may be an inch or two less; but if there is plenty of 
room, it is good practice to make it the same as the space above. 

Dampers. The general arrangement of a galvanized-iron casing 
and mixing damper is shown in Fig. 60. The cold-air duct is brought 
along the "basement ceiling from the inlet window, and connects 
with the cold-air chamber beneath the heater. The entering air passes 
up between the sections, and rises through the register above, as shown 
by the arrows. When the mixing damper is in its lowest position, 
all air reaching the register must pass through the heater; but if the 


WRO’T IRON RIPE 

Method of Hanging a Heater below a Wooden 
Floor. 
































78 


HEATING AND VENTILATION 


damper is raised to the position shown, part of the air will pass by 
without going through the heater, and the mixture entering through 
the register will be at a lower temperature than before. By changing 


FLOOR REGISTER 



GALVANIZED iron SLIDING door 
CASING 

Fig. 60. General Arrangement of a Galvantzed-Iron Casing and Mixing Damper 
Damper between Heater and Register. 

the position of the damper, the proportions of warm and cold aii 
delivered to the room can be varied, thus regulating the temperatuie 
without diminishing to any great extent the quantity of air delivered 



The objection to this form of damper is that there is a tendency for 
the air to enter the room before it is thoroughly mixed; that is, a 
stream of warm air will rise through one half of the register while 





















































HEATING AND VENTILATION 


79 


cold air enters through the other. This is especially true if the con¬ 
nection between the damper and register is short. • Fig. 61 shows 
a similar heater and mixing damper, with brick casing. Cold air is 
admitted to the large chamber below the heater, and rises through 
the sections to the register as before. The action of the mixing 
damper is the same as already described Several flues or registers 
may be connected with a stack of this form, each connection having, 
in addition to its mixing damper, an adjusting damper for regulating 
the flow of air to the different rooms. 

Another way of proportioning the air-flow in cases of this kind 
is to divide the hot-air chamber above the heater into sections, by 
means of galvanized-iron partitions, giving to each room its proper 
share of heating surface. If the cold-air supply is made sufficiently 
large, this arrangement is preferable to using adjusting dampers as 



Fig. 62. Another Arrangement of Mixing Damper and Heater in Galvanized-Iron 
Casing. Heater between Damper and Register. 


described above. The partitions should be carried down the full 
depth of the heater between the sections, to secure the best results. 

The arrangement shown in Fig. 62 is somewhat different, and 
overcomes the objection noted in connection with Fig. 60, by sub¬ 
stituting another. The mixing damper in this case is placed at the 
other end of the heater. When it is in its highest position, all of the 
air must pass through the heater before reaching the register; but 
when partially lowered, a part of the air passes over the heater, 
and the result is a mixture of cold and warm air, in proportions 
depending upon the position of the damper. As the layer of warm 
air in this case is below the cold air, it tends to rise through it, and a 
more thorough mixture is obtained than is possible with the damper 
shown in Fig. 60. One quite serious objection, however, to this form 
of damper, is illustrated in Fig. 63. When the damper is nearly 

































80 


HEATING AND VENTILATION 


closed so that the greater part of the air enters above the heater, it 
has a tendency to fall between the sections, as shown by the arrows, 
and, becoming heated, rises again, so that it is impossible to deliver 

air to a room below a certain tem¬ 
perature. This peculiar action in¬ 
creases as the quantity of air admit¬ 
ted below the heater is diminished. 
When the inlet register is placed in 
the wall at some distance above 




Fig. 63. Showing Difficulty of Regulat 
ing Temperature with Arrangement 
in Fig. 62. 


the floor, as in schoolhouse work, a thorough mixture of air can be 
obtained by plac¬ 
ing the heater so 
that the current 
of warm air will 
pass up the front 
of the flue and be 
discharged into 
the room through 
the lower part of 
the register. This 
is shown quite 
clearly in Fig. 64, 
where the cur¬ 
rent of warm air 
is represented by 
crooked arrows, 
and the cold air 
by straight ar¬ 
rows. The two 
currents pass up 
the flue separate¬ 
ly; but as soon 
as they are dis¬ 
charged through 
the register the 
warm air tends 

to rise, and the cold air to fall, with the result of a more or less 
complete mixture, as shown. 



Fig. 64. Arrangement of Heater and Damper Causing Warm Air 
to Enter Room through Lower Part of Register, thus 
Securing Thorough Mixing 



































HEATING AND VENTILATION 


81 


It is often desirable to warm a room at times when ventilation 
is not necessary, as in the case of living rooms during the night, or 
for quick warming in the morning. A register and damper for air 
rotation should be provided in this case. Fig. 05 shows an arrange¬ 
ment for this purpose. When the damper is in the position shown, 
air will be taken from the room above and be warmed over and over; 
but, by raising the damper, the supply will be taken from outside. 
Special care should be taken to make all mixing dampers tight against 
air-leakage, else their advantages will be lost. They should work 
easily and close tightly against flanges covered with felt. They may 
be operated from the rooms above by means of chains passing over 



guide-pulleys; special attachments should be provided for holding 
in any desired position. 

Warm=Air Flues. The required size of the warm-air flue between 
the heater and the register, depends first upon the difference in tem¬ 
perature between the air in the flue and that of the room, and second, 
upon the height of the flue. In dwelling-houses, where the con¬ 
ditions are practically constant, it is customary to allow 2 square 
inches area for each square foot of radiation when the room is on the 
first floor, and square inches for the second and third floors. In 
the case of hospitals, where a greater volume of air is required, these 
figures may be increased to 3 square inches for the first floor wards, 
and 2 square inches for those on the upper floors. 

In schoolhouse work, it is more usual to calculate the size of 
flue from an assumed velocity of air-flow through it. This will vary 
greatly according to the outside temperature and the prevailing wind 
conditions. The following figures may be taken as average velocities 






































82 


HEATING AND VENTILATION 


obtained in practice, and may be used as a basis for calculating the 
required flue areas for the different stories of a school building: 

1 st floor, 280 feet per minute. 

2nd “ , 340 “ “ 

3rd " , 400 “ “ 

These velocities will be increased somewhat in cold and windy weather 
and will be reduced when the atmosphere is mild and damp. 

Having assumed these velocities, and knowing the number of 
cubic feet of air to be delivered to the room per minute, we have only 
to divide this quanity by the assumed velocity, to obtain the required 
flue area in square feet. 

Example. A schoolroom on the second floor is to have an air-supply of 
2,000 cubic feet per minute. What will be the required flue area? 

Ans. 2000 -¥• 340 = 5.8 + sq. feet. 
The velocities would be higher in the coldest weather, and dampers 
should be placed in the flues for throttling the air-supply when nec¬ 
essary. 

Cold=Air Ducts. The cold-air ducts supplying heaters should 
be planned in a manner similar to that described for furnace heating. 
The air-inlet should be on the north or west side of the building; but 
this of course is not always possible. The method of having a large 
trunk line or duct with inlets on two or more sides of the building, 
should be carried out when possible. A cold-air room with large 
inlet windows, and ducts connecting with the heaters, makes a good 
arrangement for schoolhouse work. The inlet windows in this case 
should be provided with check-valves to prevent any outward flow of 
air. A detail of this arrangement is shown in Fig. 66. 

This consists of a boxing around the window, extending from 
the floor to the ceiling. The front is sloped as shown, and is closed 
from the ceiling to a point below the bottom of the window. The 
remainder is open, and covered with a wire netting of about ^-inch 
mesh; to this are fastened flaps or checks of gossamer cloth about 
6 inches in width. These are hemmed on both edges and a stout 
wire is run through the upper hem which is fastened to the netting 
by means of small copper or soft iron wire. The checks allow the air 
to flow inward but close when there is any tendency for the current 
to reverse. 

The area of the cold-air duct for any heater should be about 
three-fourths the total area of the warm-air ducts leading from it. 


HEATING AND VENTILATION 


83 


If the duct is of any considerable length or contains sharp bends, it 
should be made the full size of all the warm-air ducts. Adjusting 
dampers should be placed in the supply duct to each separate stack. 
If a trunk with two inlets is used, each inlet should be of sufficient 
size to furnish the full amount of air required, and should be pro¬ 
vided with cloth checks for preventing an outward flow of air, as 
already described. The inlet windows should be provided with 
some form of damper or slide, outside of which should be placed a 
wire grating, backed by a netting of about f-inch mesh. 

Vent Flues. In dwelling-houses, vent flues are often omitted, 
and the frequent opening of doors and leakage are depended upon to 
carry away the im¬ 
pure air. A well- 
designed system of 
warming should 
provide some means 
for discharge ven¬ 
tilation, especially 
for bathrooms and 
toilet-rooms, and 
also for living rooms 
where lights are 
burned in the even¬ 
ing. Fireplaces are 
provided in 
the more important 
rooms of a well- 
built house, a n d 
these are made to 
serve as vent flues. In rooms having no fireplaces, special flues 
of tin or galvanized iron may be carried up in the partitions in 
the same manner as the warm-air flues. These should be gathered 
together in the attic, and connected with a brick flue running up 
beside the boiler or range chimney. 

Very fair results may be obtained by simply letting the flues open 
into an unfinished attic, and depending upon leakage through the 
roof to carry away the foul air. 




Fig. 66. Air-Inlet Provided with Check-Valves to Prevent 
Outward Flow of Air. 




















84 


HEATING AND VENTILATION 


The sizes of flues may be made the reverse of the warm-air flues 
—that is, 1^ square inches area per square foot of indirect radiation 
for rooms on the first floor, and 2 square inches for those on the 
second. This is because the velocity of flow will depend upon the 
height of flue, and will therefore be greater from the first floor. The 
flow of air through the vents will be slow at best, unless some means 
is provided for warming the air in the flue to a temperature above 
that of the room with which it connects. 

The method of carrying up the outboard discharge beside a warm 
chimney is usually sufficient in dwelling-houses; but when it is 

desired to move larger 
quantities of air, a loop 
of steam pipe should be 
run inside the flue. This 
should be connected for 
drainage and air-venting 
as shown in Fig. 67. 
When vents are carried 
through the roof inde¬ 
pendently, some form of 
protecting hood should 
be provided for keeping 
out the snow and rain. 
A simple form is shown 
in Fig. 68. Flues carried 
outboard in this way 
should always be ex¬ 
tended well above the ridges of adjacent roofs to prevent down 
drafts in windy weather. 

For schoolhouse work we may assume average velocities through 
the vent flues, as follows: 

1st floor, 340 feet per minute. 

2nd “ , 280 “ “ “ 

3rd “ , 220 “ “* « 

Where flue sizes are based on these velocities, it is well to guard 
against down drafts by placing an aspirating coil in the flue. A 
single row of pipes across the flue as shown in Fig. 69, is usually 
sufficient for this purpose when the flues are large and straight 




A : r 

Valve 



uuup ui obtain mpe lo D0 nun insiae 
Connected for Drainage and Air-Venting. 
















HEATING AND VENTILATION 


85 


otherwise, two rows should be provided. The slant height of the 
heater should be about twice the depth of the flue, so that the area 


between the pipes shall equal the 
free area of the flue. 

Large vent Hues of this kind 
should always be provided with 
dampers for closing at night, and 
for regulation during strong winds. 

Sometimes it is desired to move 
a given quantity of air through a 
flue which is already in place. 
Table XXIV shows what velocities 
may be obtained through flues of 
different heights, for varying dif¬ 
ferences in temperature between the 
outside air and that in the flue. 



Fig. 68. Section Showing Simple Form 
of Protecting Hood for Vent Car¬ 
ried through Roof. 


Example .—It is desired to discharge 1,300 cubic feet of air per minute 
through a flue having an area of 4 square feet and a height of 30 feet. If the 
efficiency of an aspirating coil is 400 B. T. U., how many square feet of surface 
will be required to move this amount of air when the temperature of the room 
is 70° and the outside temperature is 60°? 



S/Z>c V/EW 



Fig. 69. Aspirating Coil Placed in Flue to Prevent Down Drafts. 


1,300 -T- 4 = 325 feet per minute = Velocity through the flue. 
Looking in Table XXIV, and following along the line opposite a 
30-foot flue, we find that to obtain this velocity there must be a differ¬ 
ence of 30 degrees between the air in the flue and the external air. 







































86 


HEATING AND VENTILATION 


If the outside temperature is 60 degrees, then the air in the flue must 
be raised to 60 + 30 = 90 degrees. The air of the room being at 
70 degrees, a rise of 20 degrees is necessary. So the problem resolves 
itself into the following: What amount of heating surface having an 

TABLE XXIV 

Air-Flow through Flues of Various Heights under Varying 
Conditions of Temperature 

(Volumes given in cubic feet per square foot of sectional area of flue) 


Height of 


Excess of Temperature of Air in Flue Above that of External Air 


r LUE 
in Feet 

5° 

10° 

15° 

20° 

30° 

50° 

5 

55 

76 

94 

109 

134 

167 

10 

77 

108 

133 

153 

188 

242 

15 

94 

133 

162 

188 

230 

297 

20 

108 

153 

188 

217 

265 

342 

25 

121 

171 

210 

242 

297 

383 

30 

133 

188 

230 

265 

325 

419 

35 

143 

203 

248 

286 

351 

453 

40 

153 

217 

265 

306 

375 

484 

45 

162 

230 

282 

325 

398 

514 

50 

171 

242 

297 

342 

419 

541 

60 

188 

264 

325 

373 

461 

594 


efficiency of 400 B. T. U. is necessary to raise 1,300 cubic feet of air 
per minute through 20 degrees? 

1,300 cubic feet per minute = 1,300 X 60 = 78,000 per hour; 
and making use of our formula for “heat for ventilation,” we have 
78,000 X 20 = 28j3G3 B T U ; 

55 

and this divided by 400 = 71 square feet of heating surface required. 

EXAMPLES FOR PRACTICE 

1. A schoolroom on the third floor has 50 pupils, who are 
4o be furnished with 30 cubic feet of air per minute each. What will 
be the required areas in square feet of the supply and vent flues? 

Ans. Supply, 3.7 +. Vent, 6.8 +. 

2. What size of heater will be required in a vent flue 40 feet 
high and with an area of 5 square feet, to enable it to discharge 1,530 
cubic feet per minute, when the outside temperature is 60°? (Assume 
an efficiency of 400 B. T. U. for the heater.) Ans. 41.7 square feet 























HEATING AND VENTILATION 


87 




Fig. 70. Section through a Floor Register. 


Registers. Registers are made of cast iron and bronze, in a 
great variety of sizes and patterns. The almost universal finish for 
cast-iron registers is black “Japan;” but they are also finished in 
colors and electroplated with 
copper and nickel. Fig. 70 
shows a section through a 
floor register, in which A rep¬ 
resents the valves, which may 
be turned in a veitical or hori¬ 
zontal position, thus opening 
or closing the register; B is the 
iron border; C, the register box 
of tin or galvanized iron; and D, the warm-air pipe. Floor registers 
are usually set in cast-iron borders, one of which is shown in Fig. 71; 
while wall registers may be screwed directly to wooden borders or 
frames to correspond with the finish of the room. Wall registers 
should be provided with pull-cords for opening and closing from the 
floor; these are shown in Fig. 72. The plain lattice pattern shown in 
Fig. 73 is the best for schoolhouse work, as it has a comparatively 

free opening for 
air-flow and is 
pleasingand sim- 
p 1 e in design. 
More elaborate 
patterns are used 
for fine dwelling- 
house work. 
Registers with 
shut-off valves 
are used for air- 
inlets, while the 
plain register 
faces without the 
valves are placed 
in the vent open¬ 
ings. The vent flues are usually gathered together in the attic, and 
a single damper may be used to shut off the whole number at once. 
Flat or round wire gratings of open pattern are often used in place of 


Fig. .71. Cast-Iron Border for a Floor Register. 





























88 


HEATING AND VENTILATION 


register faces. The grill or solid part of a register face usually takes 
up about ^ of the area; hence in computing the size, we must allow 
for this by multiplying the required “net area” by 1.5, to obtain the 
“total” or “over-all” area. 

Example. Suppose we have a flue 10 inches in width and wish to use a 
register having a free area of 200 square inches. What will be the required 
height of the register? . 

200 X 1 -5 = 300 square inches, which is the total area required; 
then 300 -s- 10 = 30, which is the required height, and we should use 
a 10 by 30-inch register. When a register is spoken of as a 10 by 



Fig. 72. Wall Register with Pull 
Cords for Opening and 
Closing. 


Fig. 73. Plain Lattice Pattern Register. Best 
for Schoolhouse Work. 


30-inch or a 10 by 20-inch, etc., the dimensions of the latticed opening 
are meant, and not the outside dimensions of the whole register. The 
free opening should have the same area as the flue with which it con¬ 
nects. In designing new work, one should provide himself with a 
trade catalogue, and use only standard sizes, as special patterns and 
sizes are costly. J ig. < 4 shows the method of placing gossamer 
check-valves back of the vent register faces to prevent down drafts, 
the same, as described for fresh-air inlets. 




























































HEATING AND VENTILATION 


89 


Inlet registers in dwelling-house and similar work are placed 
either in the floor or in the baseboard; sometimes they are located 
under the windows, just above the baseboard. The object in view 
is to place them where the currents of air entering the room will not 
be objectionable to persons sitting near windows. A long, narrow 
floor-register placed close to the wall in front of a window, sends 
up a shallow current of warm air, which is not especially noticeable 



Fig. 74. Method of Placing Gossamer Check-Valves back of Vent Register Face 

to Prevent Down Drafts. 


to one sitting near it. Inlet registers are preferably placed neat 
outside walls, especially in large rooms. Vent registers should be 
placed in inside walls, near the floor. 

Pipe Connections. The two-pipe system with dry or sealed 
returns is used in indirect heating. The conditions to be met are 
practically the same as in direct heating, the only difference being 
that the radiators are at the basement ceiling instead of on the floors 
above. The exact method of making the pipe connections will 
depend somewhat upon existing conditions; but the general method 
shown in Fig. 75 may be used as a guide, with modifications to suit 













90 


HEATING AND VENTILATION 


any special case. The ends of all supply mains should be dripped, 
and the horizontal returns should be sealed if possible. 

Pipe Sizes. The tables already given for the proportioning of 
pipe sizes can be used for indirect systems. The following table has 
been computed for an efficiency of G40 B. T. U. per square foot of 
surface per hour, which corresponds to a condensation of § of a pound 
of steam. This is twice that allowed for direct radiation in Table 



XVII; so that we can consider 1 square foot of indirect surface as 
equal to 2 of direct in computing pipe sizes. 

As the indirect heaters are placed in the basement, care must be 
taken that the bottom of the radiator does not come too near the 
water-line of the boiler, or the condensation will not flow back prop¬ 
erly; this distance, under ordinary conditions, should not be less than 
2 feet. If much less than this, the pipes should be made extra large, 
so that there may be little or no drop in pressure between the boiler 















































HEATING AND VENTILATION 


91 


TABLE XXV 


Indirect Radiating Surface Supplied by Pipes of Various Sizes 


Size of Pipe 

Square Feet of Indirect Radiation which will be Supplied with 

i Pound Drop in 200 Feet 

l Pound Drop in 100 Feet 

4 Pound Drop in 100 Feet 

1 in. 

28 

40 

57 

U “ 

51 

72 

105 

1* “ 

67 

95 

170 

2 “ 

185 

262 

375 

2$ “ 

335 

475 

675 

3 “ 

540 

775 

1, 105 

34 “ 

812 

1, 160 

1,645 

4 “ 

1, 140 

1,625 

2, 310 

5 “ 

2, 030 

2, 900 

4, 110 

6 “ 

3, 260 

4, 660 

6, 600 

7 “ 

4, 830 

6, 900 

9, 810 

8 “ 

6, 800 

9, 720 

13, 860 


and the heater. A drop in pressure of 1 pound wduld raise the 
water-line at the heater 2.4 feet. 



Pic 76 General Form of Direct-Indirect Fig. 77. Section through Radiator Shown 
b ' Radiator. In Fig. 76. 


Direct=Indirect Radiators. A direct-indirect radiator is similar 
in form to a direct radiator, and is placed in a room in the same 























































92 


HEATING AND VENTILATION 


manner. Fig. 76 shows the general form of this type of radiator; 
and Fig. 77 shows a section through the same. The shape of the 
sections is such-, that when in place, small flues are formed between 
them. Air is admitted through an opening in the outside wall; and, 
in passing upward through these flues, becomes heated before enter¬ 
ing the room. A switch-damper is placed in the duct at the base of 
the radiator, so that the air may be taken from the room itself instead 
of from out of doors, if so desired. This is shown more particularly 
in Fig. 76. 

Fig. 78 shows the wall box provided with louvre slats and netting, 
through which the air is drawn. A damper door is placed at either 

end of the radiator base; 
and, if desired, when the 
cold-air supply is shut off 
by means of the register 
in the air-duct, the radia¬ 
tor can be converted into 
the ordinary type by 
opening both damper 
doors, thus taking the air 
from the room instead 
of from the outside. It is customary to increase the size of a direct- 
indirect radiator 30 per cent above that called for in the case of 
direct heating. 



fig. 78. Wall Box with Louvre Slats and Netting, 
Direct-Indirect System. 


CARE AND MANAGEMENT OF STEAM= 
HEATING BOILERS 

Special directions are usually supplied by the maker for each 
kind of boiler, or for those which are to be managed in any peculiar 
way. The following general directions apply to all makes, and may 
be used regardless of the type of boiler employed: 

Before starting the fire, see that the boiler contains sufficient 
water. The water-line should be at about the center of the gauge- 
glass. 

The smoke-pipe and chimney flue should be clean, and the draft 
good. 

Build the fire in the usual w r ay, using a quality of coal which is 
best adapted to the heater. In operating the fire, keep the firepot 








HEATING ANI) VENTILATION 


93 


full of coal, and shake down and remove all ashes and cinders as often 
as the state of the fire requires it. 

Hot ashes or cinders must not be allowed to remain in the ashpit 
under the grate-bars, but must be removed at regular intervals to 
prevent burning out the grate. 

To control the fire, see that the damper regulator is properly 
attached to the draft doors and the damper; then regulate the draft 
by weighting the automatic lever as- may be required to obtain the 
necessary steam pressure for warming. Should the water in the 
boiler escape by means of a broken gauge-glass, or from any other 
cause, the fire should be dumped, and the boiler allowed to cool before 
adding cold water. 

An empty boiler should never be filled when hot. If the water 
gets low at any time, but still shows in the gauge-glass, more water 
should be added by the means provided for this purpose. 

The safety-valve should be lifted occasionally to see that it is 
in working order. 

If the boiler is used in connection with a gravity system, it should 
be cleaned each year by filling with pure water and emptying through 
the blow-off. If it should become foul or dirty, it can be thoroughly 
cleansed by adding a few pounds of caustic soda, and allowing it to 
stand for a day, and then emptying and thoroughly rinsing. 

During the summer months, it is l ecommended that the water 
be drawn off from the system, and that air-valves and safety-valves 
be opened to permit the heater to dry out and to remain so. Good 
results, however, are obtained by filling the heater full of water, 
driving off the air by boiling slowly, and allowing it to remain in this 
condition until needed in the fall. The water should then be drawn 
off and fresh water added. 

The heating surface of the boiler should be kept clean and free from 
ashes and soot by means of a brush made especially for this purpose. 

Should any of the rooms fail to heat, examine the steam valves 
in the radiators. If a two-pipe system, both valves at each radiator 
must be opened or closed at the same time, as required. See that 
the air-valves are in working condition. 

If the building is to be unoccupied in cold weather, draw all the 
water out of the system by opening the blow-off pipe at the boiler and 
all steam valves and air-valves at the radiators. 


94 


HEATING AND VENTILATION 


HOT=WATER HEATERS 



Types. Hot-water heaters differ from steam boilers principally 
in the omission of the reservoir or space for steam above the heating 
surface. The steam boiler might answer as a heater for hot water; 

but the large capacity left for 
the steam would tend to make 
its operation slow and rather 
unsatisfactory, although the 
same type of boiler is some¬ 
times used for both steam and 
hot water. The passages in 
a hot-water heater need not 
extend so directly from bot¬ 
tom to top as in a steam boil¬ 
er, since the problem of pro¬ 
viding for the free liberation 
of the steam bubbles does not 
have to be considered. In 
general, the heat from the 
furnace should strike the sur¬ 
faces in such a manner as to 
increase the natural circula¬ 
tion ; this may be accomplished 
to a certain extent by arrang¬ 
ing the heating surface so that 
a large proportion of the 
direct heat will be absorbed 
near the top of the heater. 
Practically the boilers for low- 
pressure steam and for hot 
water differ from each other 
very little as to the character 
of the heating surface, so that 
the methods already given for 
computing the size of grate 
surface, horse-pow r er, etc., 
under the head of “Steam 



Fig. 79. Top-—Richardson Sectional Hot-Water 
Heater. Bottom—Same Heater Equipped 
aa Steam Boiler. 

Courtesy of Richardson and Boynton, New York City. 









HEATING AND VENTILATION 


95 




Boilers,” can be used with satisfactory results in the case of hot- 
water heaters. 

It is sometimes stated that, owing to the greater difference in 
temperature between the furnace gases and the water in a hot-water 
heater, as compared with steam, the heating surface will be more 
efficient and a smaller heater can be used. While this is true to a 
certain extent, different authorities agree that this advantage is so 
small that no account should be taken of it, and the general propor¬ 
tions of the heater should be calculated in the same manner as for 
steam. Fig. 79 shows a form of heater made up of slabs or sections 
similar to the sectional steam boiler shown in Part I. The size can 
be increased in a similar manner, by adding more sections. In this 
case, however, the boiler is increased in width instead of in length. 
This has an advantage 
in the larger sizes, as 
a second fire door can 
be added, and all parts 
of the grate can be 
reached as well in the 
large sizes as in the 
small. 

Fig. 80 shows a 
boiler consisting of fire 
pot, feed section, inter¬ 
mediate reservoir, and 
a cored top. This 

boiler is circular in Fig. 80. “Standard” Boiler, with Sections Superposed. 

form and well adapted CouHesv of Giblin and Companv ' utica ' New York - 

to dwelling-houses and similar work. The cut at the left shows the 
boiler equipped for steam by the attachment of gages and water glass. 
The cut at the right shows the proper equipment for the hot-water 
system, the heater being shown in part sections to give an idea of the 
construction. 

Fig. 81 shows another type of sectional cast-iron heater. A 
deep fire chamber with corrugated sides makes this furnace a quick 
heater and keeps the fire a long time without attention. The space 
between the outer and inner corrugated shells surrounding the fur¬ 
nace, as shown by the part section in Fig. 81, is filled with water, 






96 


HEATING AND VENTILATION 


as is also the case with the cross-pipes directly over the fire and the 
drum at the top. 

The ordinary horizontal and vertical tubular boilers, with various 
modifications, are used to a considerable extent for hot-water heating, 
and are well adapted to this class of work, especially in the case of 
large buildings. 

Automatic regulators are often used for the purpose of main¬ 
taining a constant temperature of the water. They are constructed 

in different ways—some de¬ 
pend upon the expansion of a 
metal pipe or rod at different 
temperatures, and others upon 
the vaporization and conse¬ 
quent pressure of certain vol¬ 
atile liquids. These means are 
usually employed to open 
small valves which admit 
water pressure under rubber 
diaphragms; and these in turn 
are connected by means of 
chains with the draft doors 
of the furnace, and so regulate 
the draft as required to main¬ 
tain an even temperature of 
the water in the heater. Fig. 
82 shows one of the first kind. 
A is a metal rod placed in the 
flow r pipe from the heater, and 
is so connected with the valve 
B that when the water reaches 
a certain temperature the expansion of the rod opens the valve and 
admits water from the street pressure through the pipes C and D into 
the chamber E. The bottom of E consists of a rubber diaphragm, 
which is forced down by the water pressure and carries with it the 
lever which operates the dampers as shown, and checks the fire. 
When the temperature of the water drops, the rod contracts and 
valve B closes, shutting off the pressure from the chamber E. A 
spring is provided to throw the lever back to its original position, 



Fig. 81. Cast-Iron Heater Made in Sections. 
Water Fills Space Between Outer and 
Inner Shells and Drum at Top. 

Courtesy of Richardson and Boynton Company, 
New York City. 




HEATING AND VENTILATION 


9? 


and the water above the diaphragm is forced out through the pet- 
cock G, which is kept slightly open all the time. 

DIRECT HOT=WATER HEATING 

A hot-water system is similar in construction and operation to 
one designed for steam, except that hot water flows through ' the 
pipes and radiators instead. 

The circulation through the pipes is produced solely by the dif¬ 
ference in weight of the 
water in the supply and 
return, due to the differ- 
e n c e in temperature. 

When water is heated it 
expands, and thus a 
given volume becomes 
lighter and tends to rise, 
and the cooler water flows 
in to take its place; if the 
application of heat is kept 
up, the circulation thus 
produced is continuous. 

The velocity of flow de¬ 
pends upon the difference 
in temperature between 
the supply and return, 
and the height of the 
radiator above the boiler. 

The horizontal distance 
of the radiator from the 
boiler is also an important factor affecting the velocity of flow. 

This action is best shown by means of a d/agram, as in Fig. 83. 
If a glass tube of the form shown in the figure is filled with water and 
held in a vertical position, no movement of the water will be noticed, 
because the two columns A and B are of the same weight, and there¬ 
fore in equilibrium. Now, if a lamp flame be held near the tube A, 
the small bubbles of steam which are formed will show the water 
to be in motion, with a current flowing in the direction indicated by 
the arrows. The reason for this is, that, as the water in A is heated. 











































98 


HEATING AND VENTILATION 



Fig. 83. Illustrating 
How the Heating 
of Water Causes 
Circulation. 


it expands and becomes lighter for a given volume, and is forced 
upward by the heavier water in B falling to the bottom of the tube. 
The heated water flows from A through the connecting tube at the 

top, into B, where it takes the place of the 
cooler water which is settling to the bottom. If, 
now, the lamp be replaced by a furnace, and the 
columns A and B be connected at the top by 
inserting a radiator, the illustration will assume 
the practical form as utilized in hot-water heating 
(see Fig. 84). 

The heat given off by the radiator always 
insures a difference in temperature between the 
columns of water in the supply and return pipes, 
so that as long as heat is supplied by the furnace 
the flow of water will continue. The greater the 
difference in temperature of the water in the two pipes, the greater 
the difference in weight, and con¬ 
sequently the faster the flow. The 
greater the height of the radiator 
above the heater, the more rapid 
will be the circulation, because the 
total difference in weight between 
the water in the supply and return 
risers will vary directly with their 
height. From the above it is evident 
that the rapidity of flow depends 
chiefly upon the temperature differ¬ 
ence between the supply and return, 
and upon the height of the radiator 
above the heater. Another factor 
which must be considered in long 
runs of horizontal pipe is the fric¬ 
tional resistance. 

Systems of Circulation. There 
are two distinct systems of cir¬ 
culation employed—one depending 
on the difference in temperature 

of the water in the supply and return pipes, called gravity circulation ; 



Fig. 84. Illustrating Simple Clrcula 
tlon In a Heating System. 








































HEATING AND VENTILATION 


90 


and another where a pump is used to force the water through the 
mains, called forced circulation. The former is used for dwellings 
and other buildings of ordinary size, and the latter for large buildings, 
and especially where there are long horizontal runs of pipe. 

For gravity circulation some form of sectional cast-iron boiler 
is commonly used, although wrought-iron tubular boilers may be 
employed if desired. In the case of forced circulation, a heater de¬ 
signed to warm the water by means of live or exhaust steam is often 
used. A centrifugal or rotary pump is best adapted to this pur¬ 
pose, and may be driven by an electric motor or a steam engine, 
as most convenient. 

Types of Radiating Surface. Cast-iron radiators and circulation 
coils are used for hot water as 
well as for steam. Jdot-water 
radiators differ from steam 
radiators principally in having 
a horizontal passage at the top 
as well as at the bottom. 

This construction is necessary 
in order to draw off the air 
which gathers at the top of 
each loop or section. Other¬ 
wise they are the same as 
steam radiators, and are well 

adapted for the circulation of pL' or 

steam, and in some respects sage along Top. 

are superior to the ordinary pattern of steam radiator. 

The form shown in Fig. 85 is made with an opening at the top 
for the entrance of water, and at the bottom for its discharge, thus 
insuring a supply of hot water at the top and of colder water at the 
bottom. 

Some hot-water radiators are made with a cross-partition so 
arranged that all water entering passes at once to the top, from which 
it may take any passage toward the outlet. Fig. 86 is the more 
common form of radiator, and is made with continuous passages at 
top and bottom, the hot water being supplied at one side and drawn 
off at the other. The action of gravity is depended upon for making 
the hot and lighter water pass to the top, and the colder water sink 














































100 


HEATING AND VENTILATION 


to the bottom and flow off through the return. Hot-water radiators 
are usually tapped and plugged so that the pipe connections can be 
made either at the top or at the bottom. This is shown in Fig. 87. 

Wall radiators are adapted to hot-water as well as steam heating. 

Efficiency of Radiators. The efficiency of a hot-water radiator 
depends entirely upon the temperature at which the water is circu¬ 
lated. The best practical results are obtained with the water leaving 
the boiler at a maximum temperature of about 180 degrees in zero 
weather and returning at about 160 degrees; this gives an average 



Fig. 86. Common Form of Hot-Water Radiator. Circulation Fig. 87 End Elevation of 
Produced Wholly through Action of Gravity, Hot Radiator Showing Tabs 

Water Rising to Top. at Top and Bottom for 

Pipe Connections. 

temperature of 170 degrees in the radiators. Variations may be made, 
however, to suit the existing conditions of outside temperature. We 

have seen that an average cast-iron radiator gives off about 1.7 B.T.U. 

per hour per square foot of surface per degree difference in tempera¬ 
ture between the radiator and the surrounding air, when working 
under ordinary conditions; and this holds true whether it is filled 
with steam or water. 

If we assume an average temperature of 170 degrees for the 
water, then the difference in temperature between the radiator and 
the air will be 170 — 70 = 100 degrees; and this multiplied by 1.7 = 

























































































HEATING AND VENTILATION 


101 


170, which may J>e taken as the efficiency of a hot-water radiator 
under the above average conditions. 

This calls for a water radiator about 1.5 times as large as a steam 
radiator to heat a given room under the same conditions. This is 
common practice although some engineers multiply by the factor 1.6, 
which allows for a lower temperature of the water. Water leaving 
the boiler at 170 degrees should return ai about 150; the drop in 
temperature should not ordinarily exceed 20 degrees. 

Systems of Piping. A system of hot-water heating should pro¬ 
duce a perfect circulation of water from the heater to the radiating 



Fig. 88. System of Piping Usually Employed for Hot-Water Heating. 


surface, and thence back to the heater through the returns. The 
system of piping usually employed for hot-water heating is shown in 
Fig. 88. In this arrangement the main and branches have an inclina¬ 
tion upward from the heater; the returns are parallel to the mains, 
and have an inclination downward toward the heater, connecting 
with it at the lowest point. The flow pipes or risers are taken from 
the tops of the mains, and may supply one or more radiators as 
required. The return risers or drops are connected with the return 
mains in a similar manner. In this system great care must be taken 
to produce a nearly equal resistance to flow in all of the branches, so 
that each radiator may receive its full suppLv of water. It will always 



























































































102 


HEATING AND VENTILATION 


be found that the principal current of heated water will take the path 
of least resistance, and that a small obstruction or irregularity in the 
piping is sufficient to interfere greatly with the amount of heat received 
in the different parts of the same system. 

Some engineers prefer to carry a single supply main around the 
building, of sufficient size to supply all the radiators, bringing back 
a single return of the same size. Practice has shown that in general 
it is not well to use pipes over 8 or 10 inches in diameter; if larger 
pipes are required, it is better to run two or more branches. 

The boiler, if possible, should be centrally located, and branches 

carried to differ¬ 
ent parts of the 
building. This 
insures a more 
even circulation 
than if all the 
radiators are 
supplied from a 
single long main, 
in which case 
the circulation 
is liable to be 
sluggish at the 
farther end. 

The arrange¬ 
ment shown in 
Fig. 89 is similar 

to the circuit system for steam, except that the radiators have two 
connections instead of one. This method is especially adapted to 
apartment houses, where each flat has its separate heater, as it 
eliminates a separate return main, and thus reduces, by practically 
one-half, the amount of piping in the basement. The supply risers 
are taken from the top of the main; while the returns should con¬ 
nect into the side a short distance beyond, and in a direction away 
from the boiler. When this system is used, it is necessary to enlarge 
the radiators slightly as the distance from the boiler increases. 

In flats of eight or ten rooms, the size of the last radiator may be 
increased from 10 to 15 per cent, and the intermediate ones propor- 
































HEATING AND VENTILATION 


103 


tionally, at the same time keeping the main of a large and uniform 
size for the entire circuit. 

Overhead Distribution. 'This system of piping is shown in Fig. 
90. A single riser is carried directly to the expansion tank, from 
which branches are taken to supply the various drops to which the 
radiators are connected. An important advantage in connection 
with this system is that the air rises at once to thejexpansion tank, 
and escapes through the vent, so that air-valves are not required on 
the radiators. 



At the same time, it has the disadvantage that the water in the 
tank is under less pressure than in the heater; hence it will boil at 
a lower temperature. No trouble will be experienced from this, how¬ 
ever, unless the temperature of the water is raised above 212 degrees. 

Expansion Tank. Every system for hot-water heating should be 
connected with an expansion tank placed at a point somewhat above 
the highest radiator. The tank must in every case be connected to a 
line of piping which cannot by any possible means be shut off from 
the boiler. When water is heated, it expands a certain amount. 

































104 


HEATING AND VENTILATION 


depending upon the temperature to which it is raised; and a tank or 
reservoir should always be provided to care for this increase in volume. 

Expansion tanks are usually made of heavy galvanized iron of 
one of the forms shown in Figs. 91 and 92, the latter form oeing used 

where the headroom is limited. The 
connection from the heating system 
enters the bottom of the tank, and 
an open vent pipe is taken from the 
top. An overflow connected with 
a sink or drain-pipe should be 
provided. Connections should be 
made with the water supply both 
at the boiler and at the expansion 
tank, the former to be used when 
first filling the system, as by this 
means all air is driven from the bot¬ 
tom upward and is discharged 
ough the vent at the expansion 
tank. Water that is added after¬ 
ward may be supplied directly to the 
expansion tank, where the water-line can be noted in the gauge-glass. 
A ball-cock is sometimes arranged to keep the water-line in the tank 
at a constant level. 

An altitude 
gauge is often 
placed in the base¬ 
ment with the col¬ 
ored hand or point¬ 
er set to indicate 
the normal water¬ 
line in the expan- | ^ 
sion tank. When 



Fig. 91. 


A Common Form of Galvanized- 
Iron Expansion Tank. 


Yl 


VC NT PI PC 




WAT CP L/NC 


OVCBTLOW 


conaicc now 

TBOAA 

8 YSTCAA. 


Fig. 92. 


Form of Expansion Tank Used where Headroom 
is Limited. 


the movable hand 
falls below the 
fixed one, more 
water may be added, as required, through the supply pipe at the boiler. 
When the tank is placed in an attic or roof space where there is danger 
of freezing, the expansion pipe may be connected into the side of the 






































HEATING AND VENTILATION 


105 


tank, G or S inches from the bottom, and a circulation pipe taken 
from the lower part and connected with the return from an upper- 
floor radiator. This produces a slow circulation through the tank, 
and keeps the water warm. 

The size of the expansion tank depends upon the volume of 
water contained in the system, and on the temperature to which it is 
heated. The following rule for computing the capacity of the tank 
may be used with satisfactory results: 

Square feet of radiation, divided by 40, equals required capacity of 
tank in gallons. 

Air=Venting. One very important point to be kept in mind in 
the design of a hot-water system, is the removal of air from the pipes 
and radiators. When the water in the boiler is heated, the air it 
contains forms into small bubbles which rise to the highest points of the 
system. 

In the arrangement shown in Fig. 88, the main and branches 
grade upward from the boiler, so that the air finds its way into the 
radiators, from which it may be drawn off by means of the air-valves. 

A better plan is that shown in Fig. 89. In this case the expan¬ 
sion pipe is taken directly off the top of the main over the boiler, so 
that the larger part of the air rises directly to the expansion tank and 
escapes through the vent pipe. The same action takes place in the 
overhead system shown in Fig. 90, where the top of the main riser 
is connected with the tank. Every high point in the system and 
every radiator, except in the downward system with top supply con¬ 
nection, should be provided with an air-valve. 

Pipe Connections, There are various methods of connecting 
the radiators with the mains and risers. Fig. 93 shows a radiator 
connected with the horizontal flow and 'return mains, which are 
located below the floor. The manner of connecting with a vertical 
riser and return drop is shown in Fig. 94. As the water tends to 
flow to the highest point, the radiators on the lower floors should be 
favored by making the connection at the top of the riser and taking 
the pipe for the upper floors from the side as shown. Fig. 95 illus¬ 
trates the manner of connecting with a radiator on an upper floor where 
the supply is connected at the top of the radiator. 

The connections shown in Figs. 96 and 97 are used with the 
overhead system shown in Fig. 90. 


106 


HEATING AND VENTILATION 


Where the connection is of the form shown at the left in Fig. 90, 
the cooler -water from the radiators is discharged into the supply pipe 
again, so that the water furnished to the radiators on the lower floors 
is at a lower temperature, and the amount of heating surface must be 
correspondingly increased to make up for this lass, as already de¬ 
scribed for the circuit system. 




Fig. 94. Radiator Connected to Vertical 
Riser and Return Drop. 


For example, if in the case of Fig. 90 we assume the water to 
leave at 180 degrees and return at 160, we shall have a drop in tem¬ 
perature of 10 degrees on each floor; that is, the w r ater will enter the 
radiator on the second floor at 180 degrees and leave it at 170, and 
will enter the radiator on the first floor at 170 and leave it at 160. 



Fig. 95. Upper-Floor Radiator with Sup- Fig 96. Radiator Connections. Overhead 
ply Connected at Top. Distribution System. 


The average temperatures will be 175 and 165, respectively. The 
efficiency in the first case will be 175 — 70 = 105; and 105 X 1.5 = 
157. In the second case, 165 — 70 = 95; and 95 X 1.5 = 142; 
so that the radiator on the first floor will have to be larger than that 

on the second floor in the ratio of 157 to 142, in order to do the same 
work. 






























































































































































HEATING AND VENTILATION 


107 


This is approximately an increase of 10 per cent for each story 
downward to offset the cooling effect; but in practice the supply 
drops arc made of such size that only a part of the water is by-passed 
through the radiators. For this reason an increase of 5 per cent 
for each story downward is probably sufficient in ordinary cases. 

Where the radiators discharge 
into a separate return as in the case 
of Fig. 88, or those at the right in 
Fig. 90, we may assume the tempera¬ 
ture of the water to be the same on 
all floors, and give the radiators an 
equal efficiency 

In a dwelling-house of two stories, 
no difference would be made in the 
sizes of radiators on the two floors; 
but in the case of a tall office build¬ 
ing, corrections would necessarily be made as above described. 

Where circulation coils are used, they should be of a form which 
will tend to produce a flow of water through them. Figs. 98, 99, and 
100 show different ways of making up and connecting these coils. 
In Figs. 98 and 100, supply pipes may be either drops or risers; and 



Fig. 97. Another Form of Radiator 
Connection, Overhead Distribu¬ 
tion System. 



in the former case the return in Fig. 100 may be carried back, if desired, 
into the supply drop, as shown by the dotted lines. 

Combination Systems. Sometimes the boiler and piping are 
arranged for either steam or hot water, since the demand for a higher 
or lower temperature of the radiators might change. 
































































108 


HEATING AND VENTILATION 


The object of this arrangement is to secure the advantages of a 
hot-water system for moderate temperatures, and of steam heating 
for extremely cold weather. 



As less radiating surface is required for steam heating, there is 
an advantage due to the reduction in first cost. This is of consider¬ 
able importance, as a heating system must be designed of such dimen¬ 
sions as to be capable of warming a building in the coldest, weather; 



and this involves the expenditure of a considerable amount for radiat¬ 
ing surfaces, which are needed only at rare intervals. A combination 
system of hot-water and steam heating requires, first, a heater or boiler 
























































HEATING AND VENTILATION 


109 


which will answer for either purpose; second, a system of piping 
which will permit the circulation of either steam or hot water; and 
third, the use of radiators which are adapted to both kinds of heating. 
These requirements will be met by using a steam boiler provided with 
all the fittings required for steam heating, but so arranged that the 
damper regulator may be closed by means of valves when the system 
is to be used for hot-water heating. The addition of an expansion 
tank is required, which must be so arranged that it can be shut off 
when the system is used for steam heating. The system of piping 
shown in Fig. 88 is best adapted for a combination system, although 
an overhead distribution as shown in Fig. 90 may be used by shutting 
off the vent and overflow pipes, and placing air-valves on the radiators. 

While this system has many advantages in the way of cost over 
the complete hot-water system, the labor of changing from steam 
to hot water will in some cases be trouble¬ 
some; and should the connections to the 
expansion tank not be opened, serious re¬ 
sults would follow. 

Valves and Fittings. Gate-valves 
should always be used in connection with 
hot-water piping, although angle-valves may 
be used at the radiators. There are several 
patterns of radiator valves made especially 
for hot-water work; their chief advantage 
lies in a device for quick closing, usually a 
quarter-turn or half-turn being sufficient to 
open or close the valve. Two different designs are shown in Figs. 
101 and 102. 

It is customary to place a valve in only one connection, as that is 
sufficient to stop "the flow of water through the radiator; a fitting 
known as a union elbow is often employed in place of the second valve. 
(See Fig. 103.) 

Air=Valves. The ordinary pet-cock air-valve is the most reliable 
for hot-water radiators, although there are several forms of auto¬ 
matic valves which are claimed to give satisfaction. One of these 
is shown in Fig. 104. This is similar in construction to a steam 
trap. As air collects in the chamber, and the water-line is lowered, 
the float drops, and in so doing opens a small valve at the top of the 



Pig. 101. Radiator Valve lor 
Hot-Water Work. 

















110 


HEATING AND VENTILATION 


chamber, which allows the air to escape. As the water flows in to take 
its place, the float is forced upward and the valve is closed. 

All radiators which are supplied by risers from below, should be 

provided with air-valves placed in the top 
of the last section at the return end. If 
they are supplied by drops from an over¬ 




pig. 102. Another Type of Hot- 
Water Radiator Valve. 


Fig. 103. Union Elbow. 


head system, the air will be discharged at the expansion tank, and 
air-valves will not be necessary at the radiators. 

Fittings. All fittings, such as elbows, tees, etc., should be of 
the long-turn pattern. If the common form is used, they should be 

a size larger than the pipe, bushed 
down to the proper size. The long- 
turn fittings, however, are preferable, 
and give a much better appearance. 
Connections between the radiators 
and risers may be made with the 
ordinary short-pattern fittings, as 
those of the other form are not well 
adapted to the close connections nec¬ 
essary for this work. 

Pipe Sizes. The size of pipe 
required to supply any given radiator 
depends upon four conditions; first, the 
size of the radiator; second, its elevation 

F1 li o t°w a te r r adi a to r A ’ o i per ate d* ° r above the boiler; third, the length of 
by a Float. pip e required to connect it with the 

boiler; and fourth, the difference in temperature between the supply 
and the return 














































HEATING AND VENTILATION 


111 


As it would be a long and rather complicated process to work out 
the required size of each pipe for a heating system, Tables XXVI and 
XXVII have been prepared, covering the usual conditions to be met 

with in practice- 


TABLE XXVI 

Direct Radiating Surface Supplied by Mains of Different 
Sizes and Lengths of Run 



These quantities have been calculated on a basis of 10 feet difference 
in elevation between the center of the heater and the radiators, and a differ¬ 
ence in temperature of 17 degrees between the supply and the return. 

TABLE XXVII 

Radiating Surface on Different Floors Supplied by 
Pipes of Different Sizes 


Size op 
Riser 

Square Feet op Radiating Surface 

1st Story 

2d Story 

3d Story 

4th Story 

5th Story 

6th Story 

1 in 

30 

55 

65 

75 

85 

95 

1 M “ 

60 

90 

110 

125 

140 

160 

1 y 2 “ 

100 

140 

165 

185 

210 

240 

2 “ 

200 

275 

375 

425 

500 


2 M “ 

350 

475 





3 “ 

550 






3 

850 







Table XXVI gives the number of square feet of direct radiation 
which different sizes of mains and branches will supply for varying 
lengths ol run. 

Table XXVI may be used for all horizontal mains. For vertical 
risers or drops, Table XXVII may be used. This has been conn 












































112 


HEATING AND VENTILATION 


«» 

puted for the same difference in temperature as in the case of Table 
XXVI (17 degrees), and gives the square feet of surface which dif¬ 
ferent sizes of pipe will supply on the different floors of a building, 
assuming the height of the stories to be 10 feet. Where a single 
riser is carried to the top of a building to supply the radiators on the 
floors below, by drop pipes, we must first get what is called the xwerage 
elevation of the system before taking its size from the table. This may 
be illustrated by means of a diagram (see Fig. 105). 

In A we have a riser carried to the third story, and from there a 
drop brought down to supply a radiator on the first floor. The 
elevation available for producing a flow in the riser is only 10 feet, 
the same as though it extended only to the radiator. The water in 
the two pipes above the radiator is practically at the same temperature, 
and therefore in equilibrium, and has no effect on the flow of the 
water in the riser. (Actually there would be some radiation from the 
pipes, and the return, above the radiator, would be slightly cooler, but 
for purposes of illustration this may be neglected). If the radiator 
was on the second floor the elevation of the system would be 20 feet 
(see B ); and on the third floor, 30 feet; and so on. The distance 
which the pipe is carried above the first radiator which it supplies 
has but little effect in producing a flow, especially if covered, as it 
should be in practice. Having seen that the flow in the main riser 
depends upon the elevation of the radiators, it is easy to see that the 
way in which it is distributed on the different floors must be con¬ 
sidered. For example, in B, Fig. 105, there will be a more rapid 
flow through the riser with the radiators as shown, than there would 
be if they were reversed and the largest one were placed upon the first 
floor. 

We get the average elevation of the system by multiplying the 
square feet of radiation on each floor by the elevation above the 
heater, then adding these products together and dividing the same 
by the total radiation in the whole system. In the case shown in 
B, the average elevation of the system would be 
(100 X 30) + (50 X 20) + (25 X 10) 

; 100 T 50 +“25 = 24 feet; 

and we must proportion the main riser the same as though the whole 
radiation were on the second floor. Looking in Table XXVII, we 
find, for the second story, that a 1^-inch pipe will supply 140 square 



HEATING AND VENTILATION 


113 


feet; and a 2-inch pipe, 275 feet. Probably a 1^-inch pipe would 
be sufficient. 

Although the height of stories varies in different buildings, 10 
feet will be found sufficiently accurate for ordinary practice. 

INDIRECT HOT=WATER HEATING 

This is used under the same conditions as indirect steam, and 
the heaters used are similar to those already described. Special 



A B 


Pig. 105. Diagram to Illustrate Finding of Average Elevation of Heating System. 

attention is given to the form of the sections, in order that there may 
be an even distribution of water through all parts of them. As the 
stacks are placed in the basement of a building, and only a short 
distance above the boiler, extra large pipes must be used to secure a 
proper circulation, for the head producing flow is small. The stack 







































114 


HEATING AND VENTILATION 


casings, cold-air and warm-air pipes, and registers are the same as 
in steam heating. 

Types of Radiators. The radiators for indirect hot-water heating 
are of the same general form as those used for steam. Those shown 
in Figs. 52, 53, 56, 106, and 107 are common patterns. The drum 
pin, Fig. 106, is an excellent form, as the method of making the 
connections insures a uniform distribution of water through the 
stack. 

Fig. 107 shows a radiator of good form for water circulation, and 
also of good depth, whicti is a necessary point in the design of hot- 
water radiators. They should be not less than 12 or 15 inches deep 
for good results. Box coils of the form given for steam may also be 



Fig. 106. “Drum Pin” Indirect Hot-Water Radiator. 


used, provided the connections for supply and return are made of 
good size. 

Size of Stacks. As indirect hot-water heaters are used princi¬ 
pally in the wanning of dwelling-houses, and in combination with 
direct radiation, the easiest method is to compute the surfaces required 
for direct radiation, and multiply these results by 1.5 for pin radiators 
of good depth. For other forms the factor should vary from 1.5 
to 2, depending upon the depth and proportion of free area for air¬ 
flow between the sections. 

If it is desired to calculate the required surface directly by the 
thermal unit method, we may allow an efficiency of from 360 to 400 
for good types in zero weather. 

























HEATING AND VENTILATION 


115 


In schoolhouse and hospital work, where larger volumes of air 
are warmed to lower temperatures, an efficiency as high as 500 B. T. U. 
may be allowed for radiators of good form. 

Flues and Casings. For cleanliness, as well as for obtaining 
the best results, indirect stacks should be hung at one side of the 
register or flue receiving the warm air, and the cold-air duct should 
enter beneath the heater at the other side. A space of at least 10 
inches, and preferably 12, should be allowed for the warm air above 
the stack. The top of the casing should pitch upward toward the 
warm-air outlet at least an inch in its length. A space of from 8 to 

10 inches should be allowed for cold air below the stack. 

As the amount of air warmed per square foot of heating surface 
is less than in the case of steam, we may make the flues somewhat 
smaller as compared 
with the size of heater. 

The following pro¬ 
portions may be used 
under usual conditions 
for dwelling-houses: 

1^ square inches per 
square foot of radia¬ 
tion for the first floor, 

1^ square inches for 
the second floor, and 

1 1 square inches for 
the cold-air duct. 

Pipe Connections. In indirect hot-water work, it is not desirable 
to supply more than 80 to 100 square feet of radiation from a single 
connection. When the requirements call for larger stacks, they 
should be divided into two or more groups according to size. 

It is customary to carry up the main from the boiler to a point 
near the basement ceiling, where it is air-vented through a small 
pipe leading to the expansion tank. The various branches should 
grade downward and connect with the tops of the stacks. In this 
way, all air, both from the boiler and from the stacks, will find its way 
to the highest point in the main, and be carried off automatically. 

As an additional precaution, a pet-cock air-valve should be placed 
in the last section of each stack, and brought out through the casing 
by means of a short pipe. 



Fig. 107. Indirect Hot-Water Radiator. 




















116 


HEATING AND VENTILATION 


TABLE XXVIII 

Radiating Surface Supplied by Pipes of Various Sizes—Indirect Hotu 

Water System 


Diameter 

Square Feet of Radiating Surface 

Pipe 

100 Ft. Run 

200 Ft. Run 

300 Ft. Run 

400 Ft. Run 

1' in. 

15 




U “ 

30 

25 

* 


U “ 

50 

40 

25 


2 “ 

100 

75 

60 

50 

2J “ 

175 

125 

100 

90 

3 “ 

275 

200 

150 

140 

3J “ 

425 

300 

225 

200 

4 “ 

600 

425 

350 

300 

5 “ 


700 

575 

500 

6 “ 




800 

7 “ 




1,200 


Some engineers make a practice of carrying the main to the 
ceiling of the first story, and then dropping to the basement before 
branching to the stacks, the idea being to accelerate the flow of water 
through the main, which is liable to be sluggish on account of the 
small difference in elevation between the boiler and stacks. If 
the return leg of the loop is left uncovered, there will be a slight drop 
in temperature, tending to produce this result; but in any case it will 
be exceedingly small. With supply and return mains of suitable 
size and properly graded, there should be no difficulty in securing a 
good circulation in basements of average height. 

Pipe Sizes. As the difference in elevation between the stacks 
and the heater is necessarily small, the pipes should be of ample size 
to offset the slow velocity of flow through them. The sizes mentioned 
in Table XXVIII, for runs up to 400 feet, will be found to supply 
ample radiating surface for ordinary conditions. Some engineers 
make a practice of using somewhat smaller pipes, but the larger sizes 
will in general be found more satisfactory. 


CARE AND MANAGEMENT OF HOT-WATER HEATERS 


The directions given for the care of steam-heating boilers apply 
in a general way to hot-water heaters, as to the methods of caring 
for the fires and for cleaning and filling the heater. Only the special 
points of difference need be considered. Before building the fire, all 
the pipes and radiators must be full of water, and the expansion tank 
















HEATING AND VENTILATION 


117 


FORCED HOT-WATER CIRCU¬ 
LATION 



should be partially filled as indicated by the gauge-glass. Should 
the water in any of the radiators fail to circulate, see that the valves 
are*wide open and that the radiator is free from air. Water must 
always be added at the expansion tank when for any reason it is 
drawn from the system. 

The required temperature of the water will depend upon the 
outside conditions, and only enough fire should be carried to keep 
the rooms comfortably warm. Ther¬ 
mometers should be placed in the flow 
and return pipes near the heater, as a 
guide. Special forms are made for 
this purpose, in which the bulb is im¬ 
mersed in a bath of oil or mercury (see 
Fig. 108). 


While the gravity system of hot- 
water heating is well adapted to 
buildings of small and medium size, 
there is a limit to which it can be car¬ 
ried economically. This is due to the 
slow movement of the water, which 
calls for pipes of excessive size. To 
overcome this difficulty, pumps are 
used to force the water through the 
mains at a comparatively high velocity. 

The water may be heated in a 
boiler in the same manner as for 
gravity circulation, or exhaust steam 

i j?i . i . Fig. 108. Thermometer Attached to 

may be Utilized in a teed-water neater Feed-Pipe near Heater, to Deter- 
„ , . ~ „ , mine Temperature of Water. 

ot large size. Sometimes part ot the 

heat is derived from an economizer placed in the smoke passage 
from the boilers. 

Systems of Piping. The mains for forced circulation are usually 
run in one of two ways. In the two-pipe system, shown in Fig. 109, 
the supply and return are carried side by side, the former reducing 
in size, and the latter increasing as the branches are taken off. 


























118 


HEATING AND VENTILATION 


The flow through the risers is produced by the difference in 
pressure in the supply and return mains; and as this is greatest 
nearest the pump, it is necessary to place throttle-valves in the risers 
to prevent short-circuiting and to secure an even distribution through 
all parts of the system. 

Fig. 110 shows the single-pipe or circuit system. This is similar 
to the one already described for gravity circulation, except that it can 
be used on a much larger scale. 

A single main is carried entirely around the building in this 
case, the ends being connected with the suction and discharge of the 
pump as shown. 

As the pressure or head in the main drops constantly throughout 
the circuit, from the discharge of the pump back to the suction, it is 



Fig. 109. “Two-Pipe” System for Forced Hot-Water Circulation. 


evident that if a supply riser be taken off at any point, and the return 
be connected into the main a short distance along the line, there will 
be a sufficient difference in pressure between the two points to produce 
a circulation through the two risers and the connecting radiators. 
A distance of 8 or 10 feet between the connections is usually ample to 
produce the necessary circulation, and even less if the supply is taken 
from the top of the main and the return connected into the side. 

Sizes of Mains and Branches. As the velocity of flow is inde¬ 
pendent of the temperature and elevation when a pump is used, it is 
necessary to consider only the volume of water to be moved and the 
length of run. 






















HEATING AND VENTILATION 


119 


The volume is found by the equation 


in which 



R E 
500 T’ 


Q = Gallons of water required per minute; 

R — Square feet of radiating surface to be supplied; 

E = Efficiency of radiating surface in B. T. U. per sq. foot per hour; 

T = Drop in temperature of the water in passing through the heating 
system. 


In systems of this kind, where the circulation is comparatively 
rapid, it is customary to assume a drop in temperature of 30° to 40°, 
between the supply and return. 

Having determined the gallons of water to be moved, the required 
size of main can be found by assuming the velocity of flow, which 
for pipes from 5 to 8 inches in diameter may be taken at 400 to 500 


1 

i 1 

! t 

1 1 

1 


^-!». 





—- t. - 


t i 

Mt- >- 

Q) 

i rr 
x - 

• 

^ Pump 


Pig. 110. “Single-Pipe” or “Circuit” System for Forced Hot-Water Circulation. 


feet per minute. A velocity as high as 600 feet is sometimes allowed 
for pipes of large size, while the velocity in those of smaller diameter 
should be proportionally reduced to 250 or 300 feet for a 3-inch pipe. 
The next step is to find the pressure or head necessary to force the 
water through the main at the given velocity. This in general should 
not exceed 50 or 60 feet, and much better pump efficiencies will be 
obtained with heads not exceeding 35 or 40 feet. 

As the water in a heating system is in a state of equilibrium, the 
only power necessary to produce a circulation is that required to 
overcome the friction in the pipes and radiators; and, as the area of 
the passageways through the latter is usually large in comparison 
with the former, it is customary to consider only the head necessary 
to force the water through the mains, taking into consideration the 
additional friction produced by valves and fittings. 



























120 


HEATING AND VENTILATION 


Each long-turn elbow may be taken as adding about 4 feet to 
the length of pipe; a short-turn fitting, about 9 feet; 6-inch and 

4- inch swing check-valves, 50 feet and 25 feet, respectively; and 
6-inch and 4-inch globe check-valves, 200 feet and 130 feet, respec¬ 
tively. 

Table XXIX is prepared especially for determining the size of 
mains for different conditions, and is used as follows: 

Example. Suppose that a heating system requires the circulation of 480 
gallons of water per minute through a circuit main 600 feet in length. The 
pipe contains 12 long-turn elbows and 1 swing check-valve. What diameter 
of main should be used ? 

Assuming a velocity of 480 feet per minute as a trial velocity, we 
follow along the line corresponding to that velocity, and find that a 

5- inch pipe will deliver the required volume of water under a head 
of 4.9 feet for each 100 feet length of run. 

The actual length of the main, including the equivalent of the 
fittings as additional length, is 

600 + (12 x 9) + 50 = 758 feet; 

hence the total head required is 4.9 X 7.58 = 37 feet. As both 
the assumed velocity and the necessary head come within practicable 
limits, this is the size of pipe which would probably be used. If it 
were desired to reduce the power for running the pump, the size of 
main could be increased. That is, Table XXIX shows that a 6-inch 
pipe would deliver the same volume of water with a friction head of 
only about 2 feet per 100 feet in length, or a total head of 2 X 7.58 = 
15 feet. 

The risers in the circuit system are usually made the same size 
as for gravity work. With double mains, as shown in Fig. 109, they 
may be somewhat smaller, a reduction of one size for diameters over 
1^ inches being comtnon 

The branches connecting the risers with the mains may be pro¬ 
portioned from the combined areas of the risers. When the branches 
are of considerable size, the diameter may be computed from the 
available head and volume of water to be moved. 

Pumps. Centrifugal pumps are usually employed in connection 
with forced hot-water circulation, in preference to pumps of the 
piston or plunger type. They are simple in construction, having 
no valves, produce a continuous flow of water, and, for the low heads 


TABLE XXIX 

Capacity in Gallons per Minute Discharged at Velocities of 300 to 540 Feet per Minute—Also Friction Head in 

Feet, per 100 Feet Length of Pipe 


HEATING AND VENTILATION 


w 

0h 

►—I 

Oh 

Oh 

O 

05 

W 

H 

W 

W—I 

t-H 

Q 


8-1 NCH 

Friction 

1.28 

3.06 

3.82 

Capacity 

783 

1,253 

1,410 


CJ 





o 

© 

© 

CO 


4-* 



co 


CJ 




tc 

7! 


CO 


u 

£ 




4 





HH 







o 

© 

© 



o 

iO 

r- 


rt 

cd 

© 

o 


P, 





ct 



r—4 


o 





S3 





o 

o 

00 

o 


«-» 

I- 

o 

o 


o 




X 

p 

rH 

Tt< 

in 

O 

fa 




4 





h -1 





1 





<D 







o 

to 



rt 

rr 

c 

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Ph 

rf< 

t- 



cJ 





o 





C 





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tO 


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o 

o 

V-H 


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p 

Cl 


CD 

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>» 




iD 

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CD 

o 

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tO 


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rr 

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co 

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L*. 

«5 

r—! 

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p 

Cl 

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t- 

O 










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rT 







to 


Cl 


rt 

Oh 

r-H 

to 


a 

^“4 

CO 

CO 







u 





ri 

1—4 

CD 



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^■4 

F—4 


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CO 

00 

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a 

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fa 



1—4 











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♦a 






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o 

00 



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1—4 

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ct3 





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122 


HEATING AND VENTILATION 


against which they are operated, have a good efficiency. A pump of 
this type, with a direct-connected engine, is shown in big. 111. 

Under ordinary conditions the efficiency of a centrifugal pump 
falls off considerably for heads above 30 or 35 feet; but special high¬ 
speed pumps are constructed "which work with a good efficiency 
against 500 feet or more. 

Under favorable conditions an efficiency of 60 to 70 per cent is 
often obtained; but for hot-water circulation it is more common to 
assume an efficiency of about 50 per cent for the average case. 

The horse-power required for driving a pump is given by the 
following formula: 

H p = # X Vx 8.3 
' 33,000 X E ’ 

in which 

H = Friction head in feet; 

V = Gallons of water delivered per minute; 

E = Efficiency of pump. 

Centrifugal pumps are made in many sizes and with varying 
proportions, to meet the different requirements of capacity and head. 

Heaters. If the water is heated in a boiler, any good form may 
be used, the same as for gravity work. In case tubular boilers are 
used, the entire shell may be filled with tubes, as no steam space is 
required. 

In order to prevent the water from passing in a direct line from 
the inlet to the outlet, a series of baffle-plates should be used to bring 
it in contact with all parts of the heating surface. 

When steam is used for heating the water, it is customary to 
employ a closed feed-water heater with the steam on the inside of the 
tubes and the water on the outside. 

Any good form of heater can be used for this purpose by providing 
it with steam connections of sufficient size. In the ordinary form of 
heater, the feed-water flows through the tubes, and the connections 
are therefore small, making it necessary to substitute special nozzles 
of large size when used in the manner here described. 

When computing the required amount of heating surface in the 
tubes of a heater, it is customary to assume an efficiency of about 200 
B. T. U. per square foot of surface per hour, per degree difference in 
temperature between the water and steam. 




HEATING AND VENTILATION 


123 


It is usual to circulate the water at a somewhat higher tempera¬ 
ture in systems of this kind, and a maximum initial temperature of 
200 degrees, with a drop of 40 degrees in the heating system, may be 
used in computing the size of heater. If exhaust steam is used at 
atmospheric pressure, there will be a difference of 212 - 180 = -32 
degrees, between the average temperature of the water and the steam, 
giving an efficiency of 200 X 32 - 6,400 B. T, U. per square foot 
of heating surface. 

From this it is evident that 6,400 -f- 170 = 38 square feet of 
direct radiating surface, or 6,400 -r 400 = 16 square feet of indirect, 
may be supplied from each square foot of tube surface in the heater. 

Exam-pie. A building having 6,000 square feet of direct, and 2,000 
square feet of indirect radiation, is to be warmed by hot water under forced 
circulation. Steam at atmospheric pressure is to be used for heating the 
water. IIow many square feet of heating surface should the heater contain ? 

6,000 -f 38 = 158; and 2,000 
-T- 16 f= 125; therefore, 158 -f 
125 = 283 square feet, the area 
of heating surface called for. 

When the exhaust steam is 
not - sufficient for the require¬ 
ments, an auxiliary live steam 
heater is used in connection 
with it. 

EXAMPLES FOR PRACTICE 

1. A building contains 
10,000 square feet of direct 
radiation and 4,000 square feet 
of indirect radiation. How 
many gallons of water must be circulated through the mains per min- 
ute, allowing a drop in temperature of 40 degrees? Axs. 165 gal. 

2. In the above example, what size of main should be used, 
assuming the circuit to be 300 feet in length and to contain ten long- 
turn elbows? The friction head is not to exceed 10 ft., and the 
velocity of flow not to exceed 300 feet per minute. Axs. 4-inch. 

3. What horse-power will be required to drive a centrifugal 
pump delivering 400 gallons per minute against a friction head of 
40 feet, assuming an efficiency of 50 per cent for the pump? 

Axs. 8 H. P. 



Fig. Ill Centrifugal Pump Direct-Con¬ 
nected to Engine, for Forced Hot- 
Water Circulation. 

Courtesy of Jeansville Iron Works 
Company , Chicago 



124 


HEATING AND VENTILATION 


4. A building contains 10,000 square feet of direct radiation and 

5,000 square feet of indirect radiation. Steam at atmospheric pres¬ 
sure is to be used. The initial temperature of the water is to be 200°; 
and the final 160°. How many square feet of heating surface should 
the heater contain? Ans. 575 sq. ft. 

5. How many square feet would be required in the above 

heater (Example 4) if the initial temperature of the water were 180° 
and the final temperature 150°? Ans. 399 sq. ft. 

EXHAUST-STEAM HEATING 

Steam, after being used in an engine, contains the greater part 
of its heat; and if not condensed or used for other purposes, it can 
usually be employed for heating without affecting to any great extent 
the power of the engine. In general, we may say that it is a matter of 
economy to use the exhaust for heating, although various factors 
must be considered in each case to determine to what extent this is 
true. The more important considerations bearing upon the matter 
are: the relative quantities of steam required for power and for 
heating; the length of the heating season; the type of engine used; 
the pressure carried; and, finally, whether the plant under con¬ 
sideration is entirely new, or whether, on the other hand, it involves 
the adapting of an old heating system to a new plant. 

The first use to be made of the exhaust steam is the heating of 
the feed-water, as this effects a constant saving both summei and 
winter, and can be done without materially increasing the back¬ 
pressure on the engine. Under ordinary conditions, about one-sixth 
of the steam supplied to the engine can be used in this way, or more 
nearly one-fifth of the exhaust discharged from the engine. 

We may assume in average practice that about 80 per cent of 
the steam supplied to an engine is discharged in the form of steam 
at a lower pressure, the remaining 20 per cent being partly converted 
into work and partly lost through cylinder condensation. Taking 
this into account, there remains, after deducting the steam used for 
feed-water heating, .8 X { = .64 of the entire quantity of steam 
supplied to the engine, available for heating purposes. 

When the quantity of steam required for heating is small com¬ 
pared with the total amount supplied to the engine, or where the 
heating season is short, it is often more economical to run the engine 


HEATING AND VENTILATION 


125 


condensing and use the live steam for heating. This can be deter¬ 
mined in ary particular case by computing the saving in fuel by the 
use of a condenser, taking into account the interest and depreciation 
on the first cost of the condensing apparatus, and the cost of water, 
if it must be purchased, and comparing it with the cost of heating 
with live steam. 

Usually, however, in the case of office buildings and institutions, 
and commonly in the case of shops and factories, especially in north¬ 
erly latitudes, it is advantageous to use the exhaust for heating, even if 
a condenser is installed for summer use only. The principal objec¬ 
tion raised to the use of exhaust steam has been the higher back¬ 
pressure required on the engines, resulting in a loss of power nearly 
proportional to the ratio of the back-pressure to the mean effective 
pressure. There are two ways of offsetting this loss—one, by raising' 
the initial or boiler pressure; and the other, by increasing the cut¬ 
off of the engine. Engines are usually designed to work most econom¬ 
ically at a given cut-off, so that in most cases it is undesirable to 
change it to any extent. Raising the boiler pressure, on the other 
hand, is not so objectionable if the increase amounts to only a few 

V , f 

pounds. 

Under ordinary conditions in the case of a simple engine, a rise 
of 3 pounds in the back-pressure calls fcr an increase of about '5 
pounds in the boiler pressure, to maintain the same power at the 
engine. 

The indicator card shows a back-pressure of about 2 pounds 
when an engine is exhausting into the atmosphere, so that an increase 
of 3 pounds would bring the pressure up to a total of 5 pounds which • 
should be more than sufficient to circulate the steam through any 
well-designed heating system. 

If it is desired to reduce rather than increase the back-pressure, ; 
one of the so-called vacuum systems, described later, can be used. 

The systems of steam heating which have been described are 
those in which the water of condensation flows back into the boiler 
by gravity. Where exhaust steam is used, the pressure is much below ■ 
that of the boiler, and it must be returned either by a pump or by a 
return trap. The exhaust steam is often insufficient to supply the 
entire heating system, and must be supplemented by live steam taken 
directly from the boiler. This must first pass through a reducing 


126 


HEATING AND VENTILATION 


valve in order to reduce the pressure to correspond with that carried 
in the heating system. 

An engine does not deliver steam continuously, but at regular 
intervals, at the end of each stroke? and the amount.is likely to vary 
with the work done, since the governor is adjusted to admit steam in 
such a quantity as is required to maintain a uniform speed. If the 
work is light, very little steam will be admitted to the engine; and 
for this reason the supply available for heating may vary somewhat, 
depending upon the use made of the power delivered by the engine. 
In mills the amount of exhaust steam is practically constant; in 
office buildings where power is used for lighting, the variation is 
greater, especially if power is also required for the running of elevators. 

The general requirements for a successful system of exhaust 
steam heating include a system of piping of such proportions that 
only a slight increase in back-pressure will be thrown upon the engine; 
a connection which shall automatically supply live steam at a reduced 
pressure as needed; provision for removing the oil from the exhaust 
steam; a relief or back-pressure valve arranged to prevent any sudden 
increase in back pressure on the engine; and a return system of some 
kind for returning the water of condensation to the boiler against 
a higher pressure. These requirements may be met in various ways, 
depending upon actual conditions found in different cases. 

To prevent sudden changes in the back-pressure, due to irregular 
supply of steam, the exhaust pipe from the engine is often carried to 
a closed tank having a capacity from 30 to 40 times that of the engine 
cylinder. This tank may be provided with baffle-plates or other 
arrangements and may Serve as a separator for removing the oil from 
the steam as it passes through. 

Any system of piping may be used; but great care should be 
taken that as little resistance as possible is introduced at bends and 
fittings; and the mains and branches should be of ample size. Usually 
the best results are obtained from the system in which the main steam 
pipe is carried directly to the top of the building, the distributing pipes 
being run from that point, and the radiating surfaces supplied by a 
down-flowing current of steam. 

Before taking up the matter of piping in detail a few of the more 
important pieces of apparatus will be described in a brief way. 

Reducing Valves. The action of pressure-reducing valves has 


HEATING AND VENTILATION 


127 


been taken up quite fully in “Boiler Accessories,” and need not be 
repeated here. When the reduction in pressure is large, as in the 
case of a combined power and heating plant, the valve may be one or 
two sizes smaller than the low-pressure main into which it discharges. 
For example, a 5-inch valve will supply an 8-inch main, a 4-inch a 
6-inch main, a 3-inch a 5-inch main, a 2^-inch a 4-inch main, etc. 

For the smaller sizes, the difference should not be more than one 
size. All reducing valves should be provided with a valved by-pass 
for cutting out the valve in case of repairs. This connection is usually 
made as shown in plan by Fig. 112. 

Grease Extractor. When exhaust steam is used for heating pur¬ 
poses, it must first be passed through some form of separator for 
removing the oil; and as an additional precaution it is well to pass the 



BY-PASS 


Fig. 112. Connections of Reducing Valve in Exhaust-Steam Heating System 

water of condensation through a separating tank before returning it to 
the boilers. 

Such an arrangement is shown in Fig. 113. As the oil collects 
on the surface of the water in the tank, it can be made to overflow 
Into the sewer by closing the valve in the connection with the receiving 
tank, for a short time. 

As much of the oil as possible should be removed before the 
steam enters the pipes and radiators, else a coating will be formed on 
their inner surfaces, which will reduce their heating efficiency. The 
separation of the oil is usually effected by introducing a series of 
baffling plates in the path of the steam; the particles of oil striking 
these are stopped, and thus separated from the steam. The oil drops 
into a receiver provided for this purpose and is discharged through a 
trap to the sewer. 

In the separator, or extractor, shown in Fig. 114, the separation is 
accomplished by a scries of plates placed in a vertical position in the 








































128 


HEATING AND VENTILATION 


body of the separator, through which the steam must pass. These 
plates consist of upright hollow columns, *with openings at regular 
intervals for the admission of water and oil, which drain dowmward 
to the receiver below. The steam takes a zigzag course, and all of 
it comes in contact with the intercepting plates, which insures a 
thorough separation of the oil and other solid matter from the steam. 
Another form, shown in Fig. 115, gives excellent results, and has the 
advantage of providing an equalizing chamber for overcoming, to 
some extent, the unequal pressure due to the varying load on the 
engine. It consists of a tank or receiver about 4 feet in diameter, 
with heavy boiler-iron heads slightly crowned to give stiffness. 



Fig 113. Separator for Removing Oil from Exhaust Steam and Water Condensation. 

Through the center is a layer of excelsior (wooden shavings of ldng 
fibre) about 12 inches in thickness, supported on an iron grating, 
with a similar grating laid over the top to hold it in place. The 
steam enters the space below the excelsior and passes upward, as 
shown by the arrows. The oil is caught by the excelsior, which can 
be renewed from time to time as it becomes saturated. The oil and 
water which fall to the bottom of the receiver are carried off through 
a trap. Live steam may be admitted through a reducing valve, for 
supplementing the exhaust when necessary. 

Back=Pressure Valve. This is a form of relief valve which is 
placed in the outboard exhaust pipe to prevent the pressure in the 
heating system from rising above a given point. Its office is the 




















HEATING AND VENTILATION 


129 



reverse of the reducing valve, which supplies more steam when 
the pressure becomes too low. The form shown in Fig. 116 is 
designed for a vertical pipe. The valve proper consists of two discs 
of unequal area, the combined area of which equals that of the pipe. 
The force tending to open the valve is that due to the steam pressure 
acting on an area equal to the difference in area between the two discsi 
it is clear from the cut that the 
pressure acting on the larger 
disc tends to open the valve 
while the pressure on the smal¬ 
ler acts in the opposite direc¬ 
tion. The valve-stem is con¬ 
nected by a link and crank 
arm with a spindle upon which 
is a lever and weight outside. 

As the valve opens, the weight 
is raised, so that, by placing it 
in different positions on the 
lever arm, the valve will open 
at any desired pressure. 

Fig. 117 shows a different 
type, in which a spring is used 
instead of a weight. This 
valve has a single disc moving 
in a vertical direction. The 
valve stem is in the form of a 
piston or dash-pot which pre¬ 
vents a too sudden movement 
and makes it more quiet in 
its action. The disc is held 
on its seat against the steam 
pressure by a lever attached 
to the spring as shown. When 
the pressure of the steam on the underside becomes greater than the 
tension of the spring, the valve lifts and allows the steam to escape. 
The tension of the spring can be varied by means of the adjusting 
screw at its upper end. 

A back-pressure valve is simply a low-pressure safety-valve 


discharge: 


Fig. 114 


Oil Separator Consisting of Vertical 
Plates with Openings Giving Steam a 
Zigzag Course. 










































































130 


HEATING AND VENTILATION 


designed with a specially large opening for the passage of steam 
through it. These valves are made for horizontal as well as for 
vertical pipes. 


MANHOLE 




Exhaust Head. This is a form of separator placed at the top 
of an outboard exhaust pipe to prevent the water carried up in the 
steam from falling upon the roofs of buildings or in the street below. 
Fig. 118 is known as a centrifugal exhaust head. The steam, on 

entering at the bottom, is given a 
whirling or rotary motion by the 
spiral deflectors; and the water is 
thrown outward by centrifugal force 
against the sides of the chamber, from 
which it flows into the shallow trough 
at the base, and is carried away through 
the drip-pipe, which is brought down 
and connected with a drain-pipe in¬ 
side the building. The passage of the 
steam outboard is shown by the arrows. 

Fig. 116. Automatically Acting Back- „,, „ , . . . , , 

pressure Valve At tached to ver Other torms are used in which the 

water is separated from the steam by 

deflectors which change the direction of 

the currents. 

Automatic Return-Pumps. In exhaust heating plants, the 
condensation is returned to the boilers by means of some form of 
return-pump. A combined pump and receiver of the form illus- 


tical Pipe. For Preventing 
Rise of Pressure in System 
above any Desired 
Point. 



































HEATING AND VENTILATION 


131 


trated in I'ig. 119 is generally used. This consists of a cast-iron or 
wrought-iron tank mounted on a base in connection with a boiler 
feed-pump. Inside the tank is a ball-float connected by means of 
levers with a valve in the steam pipe which is connected with the 
pump When the water-line in the tank rises above a certain level, 
the float is raised and opens the steam valve, which starts the pump. 
When the water is lowered to its normal level, the valve closes and 
the pump stops. By this arrangement, a constant water-line is 
maintained in the receiver, and the pump runs only as needed to care 
for the condensation as it returns from the heating system. If dry 
returns are used, they may be brought together and connected with 
the top of the receiver. If it is desired to seal the horizontal runs, as 



Pig. 117. Back-Pressure Valve Automatic¬ 
ally Operated by a Spring. 



Pig. 118. Centrifugal Exhaust Head. 


is usually the case, the receiver may be raised to a height sufficient 
to give .the required elevation and the returns connected near the 
bottom below the water-line. 

A balance-pipe, so called, should connect the heating main with 
the top of the fank, for equalizing the pressure; otherwise the steam 
above the water would condense, and the vacuum thus formed would 
draw all the water into the tank, leaving the returns practically empty 
and thus destroying the condition sought. Sometimes an inde¬ 
pendent regulator or pump governor is used in place of a received. 
One type is shown in Fig. 120. The return main is connected at 




































132 


HEATING AND VENTILATION 


the upper opening, and the pump suction at the lower. A float inside 
the chamber operates the steam valve shown at the top, and the pump 
works automatically as in the case just described. 

If it is desired to raise the water-line, the regulator may be 
elevated to the desired height and connections made as shown in 
Fig. 121. 

Return Traps. The principle of the return trap has been de¬ 
scribed in “Boiler Accessories,” but its practical form and application 



Fig. 119. Buffalo Duplex Automatic Feed Pump and Receiver for Returning Water of 

Condensation to Boijer. 

Courtesy of Buffalo Forge Company , Buffalo , New York. 


will be taken up here. The type shown in Fig. 122 has all its working 
parts outside the trap. It consists of a cast-iron bowl pivoted at G and 
H. There is an opening through G connecting with the inside of 
the bowl. The pipe K connects through C with an interior pipe 
opening near the top (see Fig. 123). The pipe D connects with a 
receiver, into which all the returns are brought. A is a check-valve 
allowing water to pass through in the direction shown by the arrow. 
E is a pipe connecting with the boiler below the water-line. B is a 






HEATING AND VENTILATION 


133 


check opening toward the boiler, and K, a pipe connected with the 
steam main or drum. 

The action of the trap is as fol¬ 
lows : As the bowl fills with water from 
the receiver, it overbalances the 
weighted lever and drops to the bot¬ 
tom of the ring. This opens the valve 
C, and admits steam at boiler pres¬ 
sure to the top of the trap. Being at 
a higher level the water flows by grav¬ 
ity into the boiler, through the pipe E. 

Water and steam are kept from passing 
out through D by the check A. 

When the trap has emptied it¬ 
self, the weight of the ball raises it 



Fig. 120. 


Automatic Float-Operated 
Pump Governor Used instead 
of a Receiver. 


to the original position, which movement closes the valve C and opens 
the small vent F. The pressure in the bowl being relieved, water 
flows in from the receiver through D , until the trap is filled, when the 



Fig. 121. Pump Regulator Placed at Sufficient Height to Raise Water-Line to 

Point Desired. 


process is repeated. In order to work satisfactorily, the trap should 
be placed at least 3 feet above the water-level in the boiler, and the 




















































134 


HEATING AND VENTILATION 




pressure in the returns must always be sufficient to raise the water 
from the receiv'er to the trap against atmospheric pressure, which is 
theoretically about 1 pound for every 2 feet in height In practice 
there will be more or less friction to 
overcome, and suitable adjustments must 
be made for each particular case. 

Fig. 124 shows another form of trap 
acting upon the same principle, except 
that in this case the s'team valve is oper¬ 
ated by a bucket or float inside the trap. 

The pipe connections are practically the 
same as with the trap just described. 

Return traps are more commonly 
used in smaller plants where it is desired Fig . m . Return Trap with work- 
to avoid the expense and care of a pump. ing Parts External - 

Damper=ReguIators. Every heating and every power plant 
should be provided with automatic means for closing the dampers 
when the steam pressure reaches a certain point, and for opening 
them again when the pressure drops. There are various regulators 
designed for this purpose, a simple form of which is shown in Fig. 125. 

Steam at boiler pres¬ 
sure is admitted beneath a 
diaphragm which is bal¬ 
anced by a weighted lever. 
When the pressure rises to a 
certain point, it raises the 
lever slightly and opens a 
valve which admits water 
under pressure above a dia-* 
phragm located near the 
smoke-pipe. This action 
forces down a lever con¬ 
nected by chains with the 

Fig. 123. Showing Interior Detail o' Return Trap damper, and closes it. 

of Fig.!22. When the steam pressure 

drops, the water-valve is closed, and the different parts of the 
apparatus take their original positions. 

Another form similar in principle is shown in Fig. 126. In this 





HEATING AND VENTILATION 


135 


case a piston is operated by the water-pressure, instead of a diaphragm. 
In both types the pressures at which the damper shall open and close 
are regulated by suitable adjustments of the weights upon the levers. 

Pipe Connections. The method of making the pipe connections 
in any particular case will depend upon the general arrangement 
of the apparatus and the various conditions. Fig. 127 illustrates! 



Fig. 124. Return Trap with Steam Valve Operated by Bucket or Float Inside. 

the general principles to be followed, and by suitable changes may be 
used as a guide in the design of new systems. 

Steam first passes from the boilers into a large drum or header.. 
From this, a main, provided with a shut-off valve, is taken as shown; 
one branch is carried to the engines, while another is connected with 
the heating system through a reducing valve having a. by-pass and 
cut-out valves. The exhaust from the engines connects with the large 
main over the boilers at a point just above the steam drum. The 















































































































































































136 


HEATING AND VENTILATION 


branch' at the right is carried outboard through a back-pressure 
valve which may be set to carry any desired pressure on the system. 
The other branch at the left passes through an oil separator into the 
heating system. The connections between the mains and radiators 
are made in the usual way, and the main return is carried back to the 
return pump near the floor. A false water-line or seal is obtained by 
elevating the pump regulator as already described. An equalizing 



Fig. 125. Simple Form of Automatic Damper-Regulator, Operated by Lever Attached to 
Diaphragm, for Closing Dampers when Steam Pressure Reaches a Certain Point. 


or balance pipe connects the top of the regulator with the low-pressure 
heating main, and high pressure is supplied to the pump as shown. 

A sight-feed lubricator should be placed in this pipe above the 
automatic valve; and a valved by-pass should be placed around the 
regulator, for running the pump in case of aec'dent or repairs. The 
oil separator should be drained through a special oil trap to a catch- 
basin or to the sewer; and the steam drum or any other low points 



















































HEATING AND VENTILATION 


137 


or pockets in the high-pressure piping should be dripped to the 
return tank through suitable traps. 

Means should be provided for draining all parts of the system 
to the sewer, and all traps and special apparatus should be by-passed. 
The return-pump should always be duplicated in a plant of any size, 
as a safeguard against accident; and the two pumps should be run 
alternately, to make sure that one is always in working order. 



Fig. 126. Automatic Damper-Regulator Operated by Piston Actuated 

by Water ; Pressure. 


One piece of apparatus not shown in Fig. 127 is the feed-water 
heater. If all of the exhaust steam can be utilized for heating pur¬ 
poses, this is not necessary, as the cold water for feeding the boilers 
may be discharged into the return pipe and be pumped in with the 
condensation. In summertime, however, when the heating plant is 
not in use, a feed-water nearer is necessary, as a large amount-of heat 




































































































138 


HEATING AND VENTILATION 



Fig. 127. General Method of Making Pipe Connections for Exhaust-Steam Heating 























































































































HEATING AND VENTILATION 


139 


which would otherwise be wasted may lx* saved in this way. The 
connections will depend somewhat upon the form of heater used; 
but in general a single connection with the heating main inside the 
back-pressure valve is all that is necessary. The condensation from 
the heater should be trapped to the sewer. 



vacuum pump installation in was.* •?S'srr homeopathic hospital, 

SHOTTING WEBSTER SUCTION STRAINEft,^‘rtfUM GOVERNOR, An t D GAGES. 
Courtesy of Warren Webster end CYxvpmnn, Camden, New iener- 






HEATING AND VENTILATION 

PART III 


VACUUM SYSTEMS 

Low-Pressure or Vacuum Systems. In the systems of steam 
heating which have been described up to this point, the pressure 
carried has always been above that of the atmosphere, and the action 
of gravity has been depended upon to carry the water of condensation 
back to the boiler or receiver; the air in the radiators has been forced 
out through air-valves by. the pressure of steam back of it. Methods 
will now be taken up in which the pressure in the heating system is 
less than the atmosphere, and where 
the circulation through the radiators is 
produced by suction rather than by 
pressure. Systems of this kind have 
several advantages over the ordinary 
methods of circulation under pressure. 

First —no back-pressure is produced 
at the engines when used in connection 
with exhaust steam; but rather there 
will be a reduction of pressure due to 
the partial vacuum existing in the radia¬ 
tors. Second — there is a complete 
removal of air from the coils and 
radiators, so that alf portions are 
steam-filled and available for heating 
purposes. Third —there is complete drainage through the returns, 
especially those having long horizontal runs; and there is absence of 
w r ater - hammer. Fourth — smaller return pipes may be used. 

The two older systems of this kind in common use are known as the 
Webster and Paul systems; other systems of recent introduction are 
described in the Instruction Paper on Steam and Hot-Water Fitting. 

Webster System. This consists primarily of an automatic outlet- 
valve on each coil and radiator, connected with some form of suction 
apparatus such as a pump or ejector. One type of valve used is 



Fig. 128. 


Webster Air Outlet-Vrdve for 
Radiator. 

Courtesy of Warren Webster and 
Company, Camden, New Jersey. 





142 


HEATING AND VENTILATION 



Fig. 129. Webster Thermostat 
for High-Pressure Work. 
Courtesy of Warren Webster 
and Company, Camden, 

New Jersey, 


shown in section in Fig. 128, which replaces the usual hand-valve at 
the return end of the radiator. It is similar in construction to some 
of the air-valves already described, consisting of a bellows or sylphon 
which is filled with a volatile liquid; in 
the presence of the steam the liquid 
partially vaporizes, thus expanding the 
bellows so that it presses against the 
valve opening and closes it. When water 
or air fills the valve, the bellows con¬ 
tracts and allows it to be sucked out as 
shown by the arrows. 

Fig. 129 shows a thermostatic valve, 
which operates on the same principle as 
that of Fig. 128, but which is designed for 
higher pressures than are commonly used 
for heating purposes; and Fig. 130 indicates 
the method used in draining the bottoms of risers or the ends of mains. 

Fig. 131 shows another form of this valve, called a water-seal 
motor, which is used under practically the same conditions. Its 
action is as follows: 

Ordinarily, the seal A is down, and the central tube-valve is 
resting upon the seat, closing the port K and preventing direct com¬ 
munication between the interior of 
the motor-body E and the outlet 
L. The outlet is attached to a pipe 
leading to a vacuum-pump, or 
other draining apparatus, which 
exhausts the space F above the seal 
through the annular space between 
the spindle B and the inside of the 
central tube G. The water of 
condensation, accumulating in the 
radiator or coil, passes into the 
chamber E, through the inlet C, rises in the chamber, and seals the 
space between the seal-shell A and the sleeve of the bonnet D. The 
differential pressure thus created causes the seal A to rise, lifting the 
end of the central tube off the seat, thus opening a clear passageway 
for the ejection of the water of condensation. 



Fig 


rop Log 


130. Showing Method of Draining 
Bottoms of Risers or Ends 
of Mains. 
















HEATING AND VENTILATION 


143 


When all the water of condensation has been drawn out of the 
radiator, the seal and tube are reseated by gravity, thus closing the 
port K, preventing waste or loss of steam; and the pressure is equal¬ 
ized above and below the seal because of the absence of water. This 
action is practically instantaneous. When the condensation is small 
in quantity, the discharge is intermittent and rapid. 

The space between the seal A and the sleeve of the bonnet D, 
and the annular space between the central tube G and the spindle D, 


Fig. 131. Water-Seal Motor. 



form a passageway through which the air is continually withdrawn by* 
the vacuum pump or other draining apparatus. 

The action outlined continues as long as water is present. 

No adjustment whatever is necessary; the motor is entirely auto¬ 
matic. 

One special advantage claimed for this system is that the amount 
of steam admitted to the radiators may be regulated to suit the require¬ 
ments of outside temperature; and is possible without water- 
























































144 


HEATING AND VENTILATION 




Fig. 132. Typical Layout of Webster Vacuum Heating System. 
Courtesy of Warren Webster and Company, Camden, New Jersey. 













































































































































Heating and ventilation 


145 


logging or hammering. This may be done at will by closing down on 
the inlet supply to the desired degree. The result is the admission 
of a smaller amount of steam to the radiator than it is calculated to 
condense normally. The condensation is removed as fast as formed, 
by the opening of the thermostatic valve. 

The general application of this system to exhaust heating is 
shown in Fig. 132. Exhaust steam is brought from the engine as 
shown; one branch leads outboard through a back-pressure valve, 
while the other connects with the heating system through a grease 
extractor. A live steam connection is made through a reducing 
valve, as in the ordinary system. Valved connections are made 
with the coils and radiators in the usual manner; but the return 
valves are replaced by the special thermostatic valves described 
above. 

The main return is brought down to a vacuum pump which dis¬ 
charges into a return tank (not shown in the cut), where the air is 
separated from the water and passes off through a vapor pipe at the 
top. The condensation then flows into the feed-water heater, or 
receiving tank, from which it is automatically pumped back into the 
boilers. The cold-water feed supply is connected with the return 
tank, and a small cold-water jet is connected into the suction at the 
vacuum pump for increasing the vacuum in the heating system by 
the condensation of steam at this point. 

Paul System. In this system the suction is connected with the 
air-valves instead of the returns, and the vacuum is produced by 
means of a steam ejector instead of a pump. The returns are carried 
back to a receiving tank, and pumped back to the boiler in the usual 
manner. The ejector in this case is called the exhauster. 

Fig. 133 shows the general method of making the pipe connec¬ 
tions with the radiators in this system; and Fig. 134, the details of 
connection at the exhauster. 

A A are the returns from the air-valves, and connect with the 
exhausters as shown. Live steam is admitted in small quantities 
through the valves BB; and the mixture of air and steam is discharged 
outboard through the pipe C. D D are gauges showing the pressure 
in the system; and E E are check-valves. The advantage of this 
system depends principally upon the quick removal of air from the 
various radiators and pipes, which constitutes the principal obstruction 


146 


HEATING AND VENTILATION 


to circulation; the inductive action in many cases is sufficient to cause, 
the system to operate somewhat below atmospheric pressure. 

Where exhaust steam is used for heating, the radiators should 



PHUL TTSTtUP OP NCATim 


Fig. 133. Showing General Method of Making Pipe and.Radiator Connections In 

Paul System. 


be somewhat increased in size, owing to the lower temperature of 
the steam. It is common practice to add from 20 to 30 per cent to 
the sizes required for low-pressure live steam. 














































HEATING AND VENTILATION 


147 


FORCED BLAST 

In a system of forced circulation by means of a fan or blower 
the action is positive and practically constant under all usual con¬ 
ditions of outside temperature and wind action. This gives it a 
decided advantage over natural or gravity methods, which are af- 


A A 



fected to a greater or less degree by changes in wind-pressure, and 
makes it especially adapted to the ventilation and warming of large 
buildings such as shops, factories, schools, churches, halls, theaters, 
etc., where large and definite air-quantities are required. 

Exhaust Method. This consists in drawing the air out of a 
building, and providing for the heat thus carried away by placing 


































































148 


HEATING AND VENTILATION 


steam coils under windows or in other positions where ill*: inward 
leakage is supposed to be the greatest. When this method is used, a 
partial vacuum is created within the building or room, and all cu r rents 
and leaks are inward; there is nothing to govern definitely the quality 
and place of introduction of the air, and it is difficult to provide suit¬ 
able means for warming it. 

Plenum Method. In this case the air is forced into the building, 
and its quality, temperature, and point of admission are completely 
under control. All spaces are filled with air under a slight pressure, 
and the leakage is outward, thus preventing the drawing of foul air 
into the room from any outside source. But above all, ample oppor¬ 
tunity is given for properly warming the air by means of heaters, 
either in direct connection with the fan or in separate passages leading 
to the various rooms. 

Form of Heating Surface. The best type of heater for any 
particular case will depend upon the volume and final temperature 
of the air, the steam pressure, and the available space. When the 
air is to be heated to a high temperature for both warming and venti¬ 
lating a building, as in the case of a shop or mill, heaters of the general 
form shown in Figs. 135, 136, and 137 are used. These may.also be 
adapted to all classes of work by varying the proportions as required. 
They can be made shallow' and of large superficial area, for the com¬ 
paratively low temperatures used in purely ventilating w'ork; or 
deeper, with less height and breadth, as higher temperatures are 
required. 

Fig. 135 shows in section a heater of this type, and illustrates 
the circulation of steam through it. It consists of sectional cast-iron 
bases with loops of wrought-iron pipe connected as showm. The 
steam enters the upper part of the bases or headers, and passes up 
one side of the loops, then across the top and dowrn on the other side, 
where the condensation is taken off through the return drip, w r hich 
is separated from the inlet by a partition. These heaters are made 
up in sections of 2 and 4 row's of pipes each. The height varies from 
3^ to 9 feet, and the width from 3 feet to 7 feet in the standard sizes. 
They are usually made up of 1-inch pipe, although l|-inch is commonly 
used in the larger sizes: Fig. 136 shows another form, in this case 
all the loops are made of practically the same length by the special 
form of construction shown. This is claimed to prevent the short- 


HEATING AND VENTILATION 


149 


circuiting of steam through the shorter loops, which causes the outer 
pipes to remain cold. Both of these heaters are usually encased in a 




sheet-steel housing, but may be supported on a foundation between 
brick walls if desired. Another form of heater used in the same 
manner as the above is shown in Fig. 137. 

































































1 r:o HEATING AND VENTILATION 

Fig. 138 shows a special form of heater particularly adapted to 
ventilating work where the air does not have to be raised above 70 or 
80 degrees. It is inade up of 1-inch wrought-iron pipe connected 



with supply and return headers; each section contains 14 pipes, and 
they are usually made up in groups of 5 sections each. These coils 
are supported upon tee-irons resting upon a brick foundation. Heat- 


Fig. 136. Another Type of Large Coll Radiator for Mills. Factories, etc. 





























HEATING AND VENTILATION 


151 


era of this form are usually made to extend across the side of a room 
with brick walls at the sides, instead of being encased in steel housings. 

Fig. 139 shows a front view of a cast-iron sectional heater for 
use under the same conditions as the pipe heaters already described. 
This heater is made up of several banks of sections, like the one shown 
in the cut, and enclosed in a steel-plate casing. 

Cast-iron indirect radiators of the pin type are well adapted for 
use in connection with mechanical ventilation, and also for heating 



Fig. 137. Miter Hot-Blast Heatei without Casing or Connections. 

Courtesy of Buffalo Forge Company, Buffalo, New York. 

where the air-volume is large and the temperature not too high, as 
in churches and halls. They make a convenient form of heater for 
schoolhouse and similar work, for, being shallow, they can be sup¬ 
ported upon I-beams at such an elevation that the condensation will be 
returned to the boilers by gravity. 

In the case of vertical pipe heaters, the bases are below the water¬ 
line of the boilers, and the condensation must be returned by the use 
of pumps and traps. 




































152 


HEATING AND VENTILATION 


Efficiency of Pipe Heaters. The efficiency of the heaters used in 
connection with forced blast varies greatly, depending upon the 
temperature of the entering air, its velocity between the pipes, the 
temperature to which it is raised, and the steam pressure carried in 
the heater. The general method in which the heater is made up i* 
also an important factor. 

In designing a heater of this kind, care must be taken that the 
free area between the pipes is not contracted to such an extent that 
an excessive velocity will be required to pass the given quantity of 



front i //ew 


CF/L/NG L/A/F 



Fig. 138. Heater Especially Adapted to Ventilation where Air does not Have to be Heated 

above 70 to 80 degrees F. 


air through it. In ordinary work it is customary to assume a velocity 
of 800 to 1,000 feet per minute; higher velocities call for a greater 
pressure on the fan, which is not desirable in ventilating work. 

In the heaters shown, about .4 of the total area is free for the 
passage of air; that is, a heater 5 feet wide and 6 feet high would 
have a total area of 5 X 6 = 30 square feet, and a free area between 
the pipes of 30 X .4=12 square feet. The depth or number of rows 
of pipe does not affect the free area, although the friction is increased 
and additional work is thrown upon the fan. The efficiency in any 










































































HEATING AND VENTILATION 


153 


given heater will be increased by increasing the velocity of the air 
through it; but the final temperature will be diminished; that is, 
a larger quantity of air will be heated to a lower temperature in the 
second case, and, while the total heat given off is greater, the air- 
quantity increases more rapidly than the heat-quantity, which causes 
a drop in temperature. 

Increasing the number of rows of pipe in a heater, with a con¬ 
stant air-quantity, increases the final temperature of the air, but 
diminishes the efficiency of the heater, because the average difference 
in temperature between the air and the steam is less. Increasing 
the steam pressure in the 
heater (and consequently its 
temperature) increases both 
the final temperature of the 
air and the efficiency of the 
heater. Table XXX has been 
prepared from different tests, 
and may be used as a guide 
in computing probable results 
under ordinary working con¬ 
ditions. In this table it is 
assumed that the air enters 
the heater at a temperature of 
zero and passes between the 
pipes with a velocity of 800 
feet per minute. Column 1 
gives the number of rows of 
pipe in the heater, ranging 
from 4 to 20 rows; and columns 2, 3, and 4, show the final tempera¬ 
ture to which the entering air will be raised from zero under various 
pressures. Under 5 pounds pressure, for example, the rise in tem¬ 
perature ranges from 30 to 140 degrees; under 20 pounds, 35 to 150 
degrees; and under GO pounds, 45 to 170 degrees. Columns 5,6, and 
7 give approximately the corresponding efficiency of the heater. For 
example, air passing through a heater 10 pipes deep and carrying 20 
pounds pressure, will be raised to a temperature of 90 degrees, and 
the heater will have an efficiency of 1,650 B. T. U. per square foot of 
surface per hour. 



Fig. 139 
Heater 


Front View of Cast-Iron Sectional 
The Banks of Sections are En¬ 
closed in a Steel-Plato Casing. 
















154 


HEATING AND VENTILATION' 


TABLE XXX 

Data Concerning Pipe Heaters 

Temperature of entering air, zero.—Velocity of air between the pipes, 

800 feet per minute. 



Temperature to which Air will 
be Raised from Zero 

Efficiency of Heatino Surface in B T.U., 
per Square Foot per Hour 

Rows OF 







Pipe Deep 

Steam 

Pressure in 

Heater 

Steam Pressure in Heater 


5 lbs. 

20 lbs 

60 lbs. 

5 lbs. 

20 lbs. 

60 lbs. 

4 

30 

35 

45 

1,600 

1,800 

2,000 

6 

50 

55 

65 

1,600 

1,800 

2,000 

8 

65 

70 

85 

1,500 

1,650 

1,850 

10 

80 

90 

105 

1.500 

1,650 

1,850 

12 

95 

105 

125 

1,500 

1,650 

1,850 

14 

105 

120 

140 

1,400 

1,500 

1,700 

16 

120 

130 

150 

1,400 

1,500 

1,700 

18 

130 

140 

160 

1,300 

1,400 

1,600 

20 

140 

150 

170 

1,300 

1,400 

1,600 


For a velocity of 1,000 feet, multiply the temperatures given in 
the table by . 9, and the efficiencies by 1.1. 

Example. How many square feet of radiation will be required to raise 
600,000 cubic feet of air per hour from zero to 80 degrees, with a velocity 
through the heater of 800 feet per minute and a steam pressure of 5 pounds? 
What must be the total area of the heater front, and how many rows of 
pipes must it have? 

Referring back to the formula for heat required for ventilation, 
we have 


600,000 X SO 
55 


= 872,727 B.T. U. required. 


Referring to Table XXX, we find that for the above, conditions a 

heater 10 pipes deep is required, and that an efficiency of 1,500 

872,727 r __ . ■ . 

= 582 square feet of 

1,500 


B. T. U. will be obtained. Then 


surface required, which may be taken as 600 in round numbers 

600,000 mnnn w * * * • • 4 , 10,000 

——-—= 10,000 cubic feet of air per minute; and —-- = 12 5 

60 1 800 

square feet of free area required through the heater. If we assume 

.4 of the total heater front to be free for the passage of air, then 

12.5 

= 31 square feet, the total area required. 






























HEATING AND VENTILATION 


155 


For convenience in estimating the approximate dimensions of 
a heater, Table XXXI is given. The standard heaters made by dif¬ 
ferent manufacturers vary somewhat, but the dimensions given in 
the table represent average practice. Column 3 gives the square 
feet of heating surface in a single row of pipes of the dimensions given 
in columns 1 and 2; and column 4 gives the free area between the 
pipes. 


TABLE XXXI 
Dimensions of Heaters 


Width of Section 

Heioht of Pipes 

Square Feet of 
Surface 

Free Area through 
Heater in Sq. Ft. 

3 feet 

3 feet 6 inches 

20 

4.2 

3 

ii 

4 

it 

0 “ 

22 

4.8 

3 

ii 

4 

it 

6 “ 

25 

5.4 

3 

tt 

5 

it 

0 “ 

28 

6.0 

4 

it 

4 

it 

6 “ 

34 

7.2 

4 

it 

5 

tt 

0 “ 

38 

8.0 

4 

it 

5 

tt 

6 “ 

42 

8.8 

4 

tt 

6 

tt 

0 “ 

45 

9.6 

5 

it 

5 

tt 

6 “ 

52 

11 .0 

5 

it 

6 

it 

0 “ 

57 

12.0 

5 

it 

6 

it 

6 “ 

62 

13.0 

5 

it 

7 

It 

0 “ 

67 

14.0 

6 

tt 

6 

tt 

6 " 

75 

15.6 

6 

tt 

7 

it 

0 “ 

81 

16.8 

6 

tt 

7 

tt 

6 “ 

87 

18.0 

6 

it 

8 

tt 

0 “ 

92 

19.2 

7 

tt 

7 

it 

6 “ 

98 

21 .0 

7 

tt 

8 

it 

0 “ 

108 

22.4 

7 

tt 

8 

n 

6 “ 

109 

23.8 

7 

a 

9 

it 

0 “ 

116 

25.2 


In calculating the total height of the heater, add 1 foot for the 

base. 

These sections are made up of 1-inch pipe, except the last or 
7-foot sections, which are made of l|-inch pipe. 

Using this table in connection with the example just given, we 
should look in the last column for a section having a free area of 12.5 
square feet; here we find that a 5 feet by 6 feet 6 inches section has a 
free opening of 13 square feet and a radiating surface of 62 square 



































156 


heating and ventilation 




feet. The conditions call for 10 rows of pipes and 10 X 02 = 020 
square feet of radiating surface, which is slightly more than called for, 
but which would be near enough for all practical purposes. 


EXAMPLE FOR PRACTICE* 


Compute the dimensions of a heater to warm 20,000 cubic feet 
of air per minute from 10 below zero to 70 degrees above, with 5 
pounds steam pressure. 

Ans. 1,164 sq. ft. of rad. surface 10 pipes deep. 

25 sq. ft. free area through heater. 

Use twenty 5 ft. by 6 ft. sections, side by side, which gives 24 
square feet area and 1,140 square feet of surface. 

The general method of computing the size of heater for any given 
building is the same as in the case of indirect heating. First obtain 
the B. T. U. required for ventilation, and to that add the heat loss 
through walls, etc.; and divide the result by the efficiency of the 
heater under the given conditions. 

Example. An audience hall is to be provided with 400,000 cubic feet 
of air per hour. The heat loss through walls, etc., is 2.50,000 B T,U. per 
hour in zero weather. What will be the size of heater, and how many rows 
of pipe deep must it be, with 20 pounds steam pressure? 


400,000 X 70 
55 


509,090 B. T. U. for ventilation. 


Therefore 250,000 + 509,090 = 759,090 B. T. U., total to be supplied. 

We must next find to what temperature the entering air must 
be raised in order to bring in the required amount of heat, so that the 
number of rows of pipe in the heater may be obtained and its corre¬ 
sponding efficiency determined. We have entering the room for pur¬ 
poses of ventilation, 400,000 cubic feet of air every hour, at a tempera¬ 
ture of 70 degrees; and the problem now becomes: To what tem¬ 
perature must this air be raised to carry in 250,000 B. T. U. additional 
for warming? 

We have learned that 1 B. T. U. will raise 55 cubic feet of air 
1 degree. Then 250,OOO B. T. U. will raise 250,000 X 55 cubic 
feet of air 1 degree. 

250,000 X 55 „ . , 

—-— = 34 + 

400,000 

The air in this case must be raised to 70 + 34 = 104 degrees, to provide 




HEATING AND VENTILATION 


157 


for both ventilation and warming. Referring to Table XXX, we find 
that a heater 12 pipes deep will be required, and that the corre¬ 
sponding efficiency of the heater will be 1,650 B. T. U. Then 

1,650 

= 460 square feet of surface required. 

Efficiency of Cast-Iron Heaters. Heaters made up of indirect 
pin radiators of the usual depth, have an efficiency of at least 1,500 
B. T. U., with steam at 10 pounds pressure, and are easily capable of 
warming air from zero to 80 degrees or over when computed on this 
basis. The free space between the sections bears such a relation to 
the heating surface that ample area is provided for the flow of air 
through the heater, without producing an excessive velocity. 

The heater shown in Fig. 139 may be counted on for an effi¬ 
ciency at least equal to that of a pipe heater; and in computing the 
depth, one row of sections may be taken as representing 4 rows of 
pipe. 

Pipe Connections. In the heater shown in Fig. 135, all the 
sections take their supply from a common header, the supply pipe 
connecting with the top, and the return being taken from the lower 
division at the end, as shown. 

In Fig. 137 the base is divided into two parts, one for live steam, 
and the other for exhaust. The supply pipes connect with the upper 
compartments, and the drips are taken off as shown. Separate traps 
should be provided for the two pressures. 

The connections in Fig. 136 are similar to those just described, 
except that the supply and return headers, or bases, are drained 
through separate pipes and traps, there being a slight difference in 
pressure between the two, which is likely to interfere with the proper 
drainage if brought into the same one. . This heater is arranged to 
take exhaust steam, but has a connection for feeding in live steam 
through a reducing valve if desired, the whole heater being under one 
pressure. 

In heating and ventilating work where a close regulation of 
temperature is required, it is usual to divide the heater into several 
sections,depending upon its size, and to provide each with a valve in the 
supply and return. In making the divisions, special care should be 
taken to arrange for as many combinations as possible. For example, 
a heater 10 pipes deep may be made up of three sections—one of 



158 


HEATING AND VENTILATION 


2 rows, and two of 4 rows each. By means of this division, 2, 4, 6, 8, 
or 10 rows of pipe can be used at one time, as the outside weather 
conditions may require. 

When possible, the return from each section should be provided 
with a water-seal two or three feet ; n depth. In the case of overhead 
heaters, the returns may be sealed by the water-line of the boiler or 
by the use of a special water-line trap; but vertical pipe heaters 
resting on foundations near the floor are usually provided with siphon 
loops extending into a pit. If this arrangement is not convenient, a 
separate trap should be placed on the return from each section. 
The main return, in addition to its connection with the boiler or 



Fig. 140. Heater Made Up of Interchangeable Sections. 


pump receiver, should have a connection with the sewer for blowing 
out when steam is first turned on. Sometimes each section is pro¬ 
vided with a connection of this kind. 

Large automatic air-valves should be connected with each 
section; and it is well to supplement these with a hand pet-cock, 
unless individual blow-off valves are provided as described above. 

If the fan is driven by a steam engine, provision should be made 
for using the exhaust in the heater; and part of the sections should 
be so valved that they may be supplied with either exhaust or live 
steam. 

































HEATING AND VENTILATION 


(159 


Fig. 140 shows an arrangement in which all of the sections are 
interchangeable. 

From 50 to 60 square feet of radiating surface should be provided 
in the exhaust portion of the heater for each engine horse-power, 
and should be divided into at least three sections, so that it can be 
proportioned to the requirements of different outside temperatures. 

Pipe Sizes. The sizes of the mains and branches may be com¬ 
puted from the tables already given in Part II, taking into account 
the higher efficiency of the heater and the short runs of piping. 

Table XXXII, based on experience, has been found to give 
satisfactory results when the apparatus is near the boilers. If the 
main supply pipe is of considerable length, its diameter should be 
checked by the method previously given. 

TABLE XXXII 
Pipe Sizes 


Square Feet or Surface 

Diameter of Steam Pipe 

Diameter of Return 

150 

2 inches 

14 inches 

300 

2* “ 

H “ 

500 

3 “ 

2 

700 

3i “ 

2 

1,000 

4 

24 “ 

2,000 

5 

24 “ 

3,000 

6 

3 


Heaters of the patterns shown in Figs. 135, 136, and 137 are 
usually tapped at the factory for high or low pressure as desired, 
and these sizes may be followed in making the pipe connections. 

The sizes marked on Fig. 136 may be used for all ordinary work 
where the pressure runs from 5 to 20 pounds; for pressures above 
that, the supply connections may be reduced one size. 

FANS 

There are two types of fans in common use, known as the cm- 
trifugal Jan or blower, and the disc fan or 'proyeller. The former 
consists of a number of straight or slightly curved blades extending 
radially from an axis, as shown in Fig. 141. When the fan is in 
motion, the air in contact with the blades is thrown outward by the 
action of centrifugal force, and delivered at the circumference or 













160 


HEATING AND VENTILATION 


periphery of the wheel. A partial vacuum is thus produced at the 
center of the wheel, and air from the outside flows in to take the 
place of that which has been discharged. 

Fig. 142 illustrates the action of a centrifugal fan, the arrows 
showing the path of the air. 

This type of fan is usually 
enclosed in a steel - plate 
casing of such form as to 
for the free move¬ 
ment of the air as it es¬ 
capes from the periphery 
of the wheel. An opening 
in the circumference of the 
casing serves as an outlet 
into the distributing ducts 
which carry the air to the 
various rooms. Another 
type of centrifugal fan, 
known as the “Conoidal” 
fan, is shown in Fig. 143, 
and a type of “multivane” 
fan, direct-connected to a steam turbine, is shown in Fig. 144. 

The discharge opening can be located in any position desired, 
either up, down, top horizontal, bottom horizontal, or at any angle. 

Where the height of the fan room is 
limited, a form called the three-quarter 
housing may be used, in which the lower 
part of the casing is replaced by a brick 
or cemented pit extending below the floor- 
level as shown in Fig. 145. 

Another form of centrifugal fan is 
shown in Fig. 146. This is known as the 
cone fan, and is commonly placed in an 
opening in a brick wall, and discharges air 
from its entire periphery into a room called 
a 'plenum chamber, with which the various 
distributing ducts connect. 

This fan is often made double by placing two wheels back to 



of Centrifugal Fan. The 
Arrows Show the Path of 
the Air. 




Fig. 141. Centrifugal Fan or Blower. 











HEATING AND VENTILATION 


161 


back and surrounding them with a steel casing. In the conoidal 
fan which is shown in Eig. 143, the casing has been removed. 

Cone fans are particularly adapted to church and schoolhouse 
work, as they are capable of moving large volumes of air at moderate 
speeds, thus providing adequate ventilation without causing an 
influx of cold air. 

Fig. 147 shows a form of small direct-connected exhauster com¬ 
monly used for ventilating toilet-rooms, chemical hoods, etc. This 
exhauster is driven by an electric motor and is of the up-discharge 
type. 

Centrifugal fans are used almost exclusively for supplying air 
for the ventilation of buildings, and for forced-blast heating. They 
are also used as exhausters for 
removing the air from buildings in 
cases where there is considerable 
resistance due to the small size or 
excessive length of the discharge 
ducts. 

General Proportions. The gen¬ 
eral form of a fan wheel is shown 
in Fig. 141, which represents a 
single spider wheel with curved 
blades. Those over 4 feet in diam¬ 
eter usually have two spiders, while 
fans of large size are often provided 
with three or more. The number 
of floats or blades commonly varies 
from six to twelve, depending upon 
the diameter of the fan. They 

are made both curved and straight; the former, it is claimed, run 
more quietly, but, if curved too much, will not work so well against 
a high pressure as the latter form. 

The relative proportions of a fan wheel vary somewhat in the 
case of different makes. The following are averages taken from fans 
of different sizes as made by several well-known manufacturers for 

general ventilating and similar work: 

Width of fan at center = Diameter X .52 

Width of fan at perimeter = Width at center X .8 

Diameter of inlet = Diameter of wheel X .68 



Fig. 143. Conoidal Fan without Casing. 
Courtesy of Buffalo Forge Company, 
Buffalo, New York. 


t 


162 HEATING AND VENTILATION 



Fig. 144. “Multivane” Fan with Direct-Connected Turbine. 
Courtesy of B. F. Sturtevant Company, Hyde Park, Massachusetts. 



Kg. 145. Steel Plate Steam Fan with Three-Quarter Housing and Single. 

Upright Engine 

Courtesy of B. F. Sturtevant Company, Hyde Park, Massachusetts. 



















HEATING AND VENTILATION 


163 


Fans are made both with double and with single inlets, the 
former being called blowers and the latter exhausters. . The size of 
a fan is commonly expressed in inches, which means the approximate 
height of the casing of a full-housed fan. The diameter of the wheel 
is usually expressed in feet, and can be found in any given case by 
dividing the size in inches by 20. For example, a 120-inch fan has a 
wheel 120 -r 20 = 6 feet in diameter. 



Fie 146 “Cone” Fan. Discharges through Opening in Wall intoa “Plenum Chamber r 

Connecting with Distributing Ducts. 


Theory of Centrifugal Fans. The action of a fan is affected 
to such an extent by the various conditions under which it operates, 
that it is impossible to give fixed rules for determining the exact 
results to be expected in any particular instance. This being the 
case, it seems best to take up the matter briefly from a theoretical 



164 


HEATING AND VENTILATION 



standpoint, and then show what corrections are necessary in the 
case of a given fan under actual working conditions. 

There are various methods for determining the capacity of a 
fan at different speeds, and the power necessary to drive it; each 
manufacturer has his own formulae for this purpose, based upon 
tests of his own particular fans-. The methods given here apply 
in a general way to fans having proportions which represent the 
average of several standard makes; and the results obtained will be 


Fig. 147. Motor-Driven Exhauster for Ventilating Toilet-Rooms, Chemical Hoods, etcj 

Courtesy of Buffalo Forge Company, Buffalo, 

found to correspond well with those obtained in practice under 
ordinary conditions. 

As already stated, the rotation of a fan of this type sets in motion 
the air between the blades, which, by the action of centrifugal force, 
is delivered at the periphery of the wheel into the casing surrounding 
it. As the velocity of flow through the discharge outlet depends 
upon the pressure or head within the casing, and this in turn upon 
the velocity of the blades, it becomes necessary to examine briefly 
into the relations existing between these quantities. 



HEATING AND VENTILATION 


165 


Pressure. The pressure referred to in connection with a fan, 
is that in the discharge outlet, and represents the force which drives 
the air through the ducts and flues. The greater the pressure with a 
given resistance in the pipes, the greater will be the volume of air 
delivered; and the greater the resistance, the greater the pressure 
required to deliver a given quantity. 

The pressure within a fan casing is caused by the air being 
thrown from the tips of the blades, and varies with the velocity of 
rotation; that is, the higher the speed of the fan, the greater will be 
the pressure produced. Where the dimensions of a fan and casiYig 
are properly proportioned, the velocity of air-flow through the outlet 
will be the same as that of the tips of the blades, and the pressure 
within the casing will be that corresponding to this velocity. 

Table XXXIII gives the necessary speed for fans of different 
diameters to produce different pressures, and also the velocity of air¬ 
flow due to these pressures. 

TABLE XXXIII 


Fan Speeds, Pressures, and Velocities of Air-Flow 


S8URE, IN 
NCE8 PER 

q Inch 



Diameter cf Fan Wh 

eel, in Feet 


h 

u] y 

O u H 

G =£ 

S g. 

3 

1 4 

5 

G 

7 

8 

*9 

10 











a O a 




F. 

V O LUTIO NS PE It 

Minute 



> J B. 
bi 

i 

274 

206 

164 

137 

117 


103 

92 

82 

2,585 

i 

336 

252 

202 

168 

144 


126 

112 

101 

3,165 

i 

3.38 

291 

232 

194 

106 


146 

129 

116 

3,653 

1 

433 

325 

260 

217 

186 


163 

144 

130 

4,084 


The application of this table will be made plain by a brief dis¬ 
cussion of blast area. 

Blast Area. When the outlet from a fan casing is small, the air 
will pass out with a velocity equal to that of the tips of the blades; and 
the pressure within the casing will be that corresponding to the 
tip velocity. That is, a 3-foot fan wheel revolving at a speed of 274 
revolutions per minute will produce a pressure within the fan casing 
of } ounce per square inch, and will cause a velocity of flow through 
the discharge outlet of 2,585 feet per minute (see Table XXXIII). 





























166 


HEATING AND VENTILATION 


Now, if the opening be slowly increased, while the speed of the fan 
remains constant, the air will continue to flow with the same velocity 
until a certain area of outlet is reached. If the outlet he still further 
increased, the pressure in the casing will begin to drop, and the 
velocity of outflow become less than the tip velocity. The effective 
area of outlet at the point when this change begins to take place, is 
called the blast area or capacity area of the fan. This varies some¬ 
what with different types and makes of fans; but for the common 
form of blower, it is approximately ^ of the projected area of the fan 

opening at the periphery—that is, in which D is the diameter 

of the fan wheel, and w its width at the periphery. It has already 

been stated under “General Proportions” that W = .52 D, and w — .8 

tt/ ., . . Dx.SfV DX.SX.52D n2 

\V ; so that we may write A = ---=--- = .14 D, 


in which A = the blast area, and D the diameter of the fan. 

As a matter of fact, the outlet of a fan casing is always made 
larger than the blast area; and the result is that the pressure drops 
below that due to the tip velocity, and the velocity of flow through 
the outlet becomes less than that given in the last column of Table 
XXXIII for any given speed of fan. 

Effective Area of Outlet. The size of discharge outlet varies 
somewhat for different makes; but for a large number of fans ex¬ 
amined it was found to average about 2.22 times the blast area 
as computed by the above method. When air or a liquid flows 
through an orifice, the stream is more or less contracted, depending 
upon the form of the orifice. 

In the case of a fan outlet, the effective area may be taken as about 
8 of the actual area. This makes the effective area of a fan outlet 
equal to .8 X 2.22 = 1.7S times the blast area. 

Table XXXIV gives the effective areas of fans of different 
diameter as computed by the above method. That is, Effective 
area = .14Z> 2 X 1.78 = .25 D\ 

Speed. We have seen that when the discharge outlet is made 
larger than the blast area, the pressure within the fan casing drops 
below that due to the tip velocity; so that, in order to bring the pres¬ 
sure up to its original point, the speed of the fan must be increased 
above that given in Table XXXIII. 





HEATING AND VENTILATION 


167 


TABLE XXXIV 
Effective Areas of Fans 


Diameter of Fan, in Feet 

Effective Area of Outlet, in 
Square Feet 

3 

2.3 

4 

4.0 

'5 

6.3 

6 

9.1 

7 

12.3 

8 

16.0 

9 

20.4 

10 

25.2 


Tests upon a fan of practically the same proportions as those 
previously given, shovv that, when the effective outlet area is made 
1.78 the blast area, the speed must be increased 1.2 times in order 
to keep the pressure at the same point as when the outlet is equal 
to or less than the blast area. 

Capacity. The capacity of a fan is the volume of air discharged 
in a given time, and is usually expressed in cubic feet per minute. 
It is equal to the effective area of discharge multiplied by the velocity 
of flow through it. 

Example. At what speed must a 6-foot fan be run to maintain a pres¬ 
sure of } ounce, and what volume of air will be delivered per minute? 

From Table XXXIII we find that a 6-foot fan must run at a 
speed of 194 revolutions per minute to maintain the given pressure 
when the outlet is equal to the blast area, or 194 X 1-2 = 233 revo¬ 
lutions per minute under actual conditions. • The velocity of flow 
through the outlet at \ ounce pressure, is 3,653 feet per minute (Table 
XXXIII); and the effective area of outlet of a 6-foot fan is 9.1 square 
feet (Table XXXIV). Therefore the volume of air delivered per 
minute is equal to 9.1 X 3,653 = 33,242 cubic feet. 

Example. It is desired to move 52,000 cubic feet of air per 
minute at a pressure of \ oun«e. What size and speed of fan will 
be required? Looking iln Table XXXIII, we find that the velocity 
through the fan outlet for 1-ounce pressure is 2,585, which calls for 
an outlet area of 52,000 -h 2,585 = 20.1 square feet. Looking in 
Table XXXIV, we find this corresponds very nearly to a 9-foot fan, 
which is the size called for. Referring again to Table XXXIII, the 
speed necessary to maintain the required pressure under the given 
conditions is found to be 92 X 1.2 = 110 revolutions per minute. 










168 


HEATING AND VENTILATION 


Effect of Resistance. Thus far it has been assumed that the 
fan was discharging into the open air against atmospheric pressure. 
The effect of adding a resistance by connecting it with a series of 
ventilating ducts, is the same as partially closing the discharge outlet. 
Carefully conducted tests upon this type of fan have shown that the 
reduction of air-flow is very nearly in proportion to the reduction 
of the discharge area. That is, if the outlet of the fan is closed to 
one-half its original area, the quantity of air discharged will be prac¬ 
tically one-half that delivered by the fan with a free opening. The 
effect of attaching a fan to the ventilating flues of a building like a 
schoolhouse, church, or hall, where the ducts have easy bends and 
where the velocity of airtflow through them is not over 1,000 to 1,200 
leet per minute, is about the same as reducing the outlet 20 per cent. 
For factories with deep heaters and smaller ducts, where the velocity 
runs up to 1,500 or 1,800 feet per minute, the effect is equivalent to 
closing the outlet at least 30 per cent, and even more in very large 
buildings. 

For schoolhouses and similar work a fan should not be run much 
above the speed necessary to maintain a pressure of § ounce at the 
outlet. Higher speeds are accompanied with greater expenditure of 
power, and are likely to produce a roaring noise or to cause vibration. 
A much lower speed does not provide sufficient pressure to give proper 
control of the air-distribution during strong winds. For factories, 
a higher pressure of § to f ounce is more generally employed. 

Actually the pressure is increased slightly by restricting the out¬ 
let at constant speed; but this is seldom taken into account in venti¬ 
lating work, as volume, speed, atid power are the quantities sought. 

Example. A school building requires 32,000 cubic feet of air per min¬ 
ute. What size and speed of fan will be required? 

If the resistance of the ducts and flues is equivalent to cutting 
down the discharge outlet 20 per cent, we must make the computa¬ 
tions for a fan which will discharge 32,000 .8 = 40,000 cubic feet 

in free air. 

Looking in Table XXXIII, we find the velocity for f-ounce 
pressure to be 3,165 feet per minute; therefore the size of fan outlet 
must be 40,000 -r 3,165 = 12.6 square feet, which, from Table 
xxxrv, we find corresponds very nearly to a 7-foot fan. 


HEATING AND VENTILATION 


169 


Referring again to Table XXXIII, the required speed is found 
to be 144 X 1.2 = 173 revolutions per minute. 

Example. A factory requires 21,000 cubic feet of air per minute for 
warming and ventilating. What size and speed of fan will be required? 

21,000 -i- .7 — 30,000, the volume to provide for with a fan 
discharging into free air. Assuming a pressure of f ounce, the veloc¬ 
ity will be 4,084 feet per minute, from which the area of outlet is 
found to be 30,000 -f- 4,084 = 7.3 square feet. This, we find, does 
not correspond to any of the sizes given in Table XXXIV. As 
standard fans are not usually made in half-sizes above 5 feet, we 
shall use a 5-foot fan and run it at a higher speed. 

A 5-foot fan has an outlet area of 6.3 square feet, and at f-ounce 
pressure it would deliver 6.3 X 4,084 = 25,729 cubic feet of air per 
minute, at a speed of 260 X 1.2 = 312 revolutions per minute. 
The volume of air delivered by a fan varies approximately as the 
speed; so, in order to bring the volume up to the required 30,000, the 
speed must be increased by the ratio 30,000 25,729 = 1.16, 

making the final speed 312 X 1.16 = 362 revolutions per minute. 
In the same way, a 6-foot fan could have been used and run at a 
proportionally lower speed. 

Power Required. The work done by a fan in moving air is 
represented by the pressure exerted, multiplied by the distance through 
which it acts. 

Table XXXV gives the horse-power required for moving the 
air which will flow through each square foot of the effective outlet 
area, under different pressures. 

This table gives only the power necessary for moving the air, 
and does not take into consideration the friction of the air in passing 
through the fan, nor that of the fan itself. 

The efficiency of a fan varies with the speed, the size of outlet, 
and the pressure against which the fan is working. Under favorable 
conditions, with properly proportioned fans, we may count on an 
efficiency of about .35. 

Example. What horse-power will be required to drive an 8-foot fan at 
such a speed as to maintain a pressure of I ounce? 

An 8-foot fan has an outlet area of 16 square feet (Table XXXIV); 
and from Table XXXV we find that .5 horse-power is required to 
move the air which will flow through each square foot of outlet under 




170 


HEATING AND VENTILATION 


TABLE XXXV 


Power Required for Moving Air under Different Pressures 


Pressure in Ounces per Square Inch 

Horse-Power for Moving Air which will 
Flow through Each Square Fqot of 
Effective Outlet*Area 

I 

.18 

a 

.33 

h 

.50 

% 

.70 


^-ounce pressure. Therefore the power required to move the air 
alone is 16 X .5 = 8, and the total horse-power is 8 .35 = 23. 

Effect of Resistance . In the above case, it is assumed that the 
fan is discharging into free air. If a resistance is added, the effect 
is "the same as partially closing the outlet, and the volume of air 
moved and the horse-power required are both reduced in very nearly 
the same proportion. This reduction, as already stated, may be 
taken as 20 per cent for schoolhouse and similar work, and 30 per 
cent for factories. 


For example, if the fan just considered was to be used for venti¬ 
lating a schoolhouse, delivering air under a pressure of £ ounce, the 
necessary horse-power would be only 23 X .8 = 18.4. If used for 
a factory, delivering air under a pressure of f ounce, the required 


horse-power would be ^ ^ 


s 


General Rules. The methods above described may be briefly 
expressed as follows: 

Capacity— Q = A X v X F, in which 
Q = Cubic feet of air per minute; 

A = Effective area of fan outlet (Table XXXIV); 
v = Velocity of flow through outlet; 

3,165 (J-ounce pressure) for schoolhouses, etc.; 

4,084 (f-ounce pressure) for factories; 

.8 for schoolhouses, etc.; 

.7 for factories. 

Speed Take the speed from Table XXXIII, corresponding to the given 
pressure and size of fan, and multiply by 1 

Horse-Power—H.P. = F , in which 

.OD 

H.P. = Horse-power; 

A = Effective area of fan outlet; 

V = Horse-power to move air which will flow through 1 square foot of fan 
outlet under given pressure (Table XXXV); 












HEATING AND VENTILATION 


171 


| .33 for schoolhouses, etc.; 
) .7 for factories, 
j .8 for schoolhouses, etc.; 

1-7 


for factories. 


EXAMPLES 


1. A schoolhouse requires an air-supply of 30,000 cubic feet 

per minute. What will be the required size of fan, its speed, and 
the H. P. of engine to drive it? f 7 ft. in diameter. 

Ans. - 173 r. p. m. 

.9 H.P. 

2. What will be the size and speed of fan, and horse-power of 
engine, to heat and ventilate a factory requiring 1,080,000 cubic feet 


of air per hour? 


Ans. 


6 ft. in diameter. 
260 r. p. m. 

8.8 H.P. 


General Relations. The following general relations between the 
volume, pressure, and power will often be found useful in deciding 
upon the size of a fan: 

(1) The volume of air delivered varies directly as the speed of the fan, 
that is, doubling the number of revolutions doubles the volume of air de¬ 
livered. 

(2) The pressure varies as the square, of the speed. For example, if 
the speed is doubled, the pressure is increased 2X2=4 times; etc. 

(3) The power required to run the fan varies as the cube of the speed. 
Thus, if the speed is doubled, the power required is increased 2 X 2 X 2 = 8 
times; etc. 


The value of a knowledge of these relations may be illustrated 
by the following example: 

Suppose for any reason it were desired to double the volume of 
air delivered by a certain fan. At first thought we might decide to 
use the same fan and run it twice as fast; but when we come to con¬ 
sider the power required, we should find that this would have to be 
' increased 8 times, and it would probably be much cheaper in the 
long run to put in a larger fan and run it at low r er speed. 

Disc or Propeller Fans. When air is to be moved against a very 
slight resistance, as in the case of exhaust ventilation, the disc or pro¬ 
peller type of wheel may be used. This is shown in different forms 
in Figs. 149 and 150. This type of fan is light in construction, re¬ 
quires but little power at low speeds, and is easily erected. It may be 










172 


HEATING AND VENTILATION 


conveniently placed in the attic or upper story of a building, where 
it may be driven either by a direct- or belt-connected electric motor. 
Fig. 148 shows a fan equipped with a direct-connected motor, and 
Fig. 151 the general arrangement when a belted motor is used. These 
fans are largely used for the ventilation of toilet and smoking rooms, 
restaurants, etc., and are usually mounted in a wall opening, as shown 
in Fig. 151. A damper should always be provided for shutting off 
the opening when the fan is not in use. The fans shown in Figs. 149 
and 150 are provided with pulleys for belt connection. 



Fig. 1 »8. Propeller Fan Direct-Connected to Motor. 


Fans of this kind are often connected with the main vent flues 
of large buildings, such as schools, halls, churches, theaters, etc., 
and are especially adapted for use in connection with gravity heating 
systems. They are usually run by electric motors, and as a rule are 
placed in positions where an engine could not be connected. and also 
in buildings where steam pressure is not available. 

Capacity of Disc bans. The capacity of a disc fan varies greatly 
with the type and the conditions under which it operates. The rated 





















HEATING AND VENTILATION 


173 


capacities usually given in catalogues are for fans revolving in free 
air—that is, mounted in an opening without being connected with 
ducts or subjected to other frictional resistance. 

As the capacity and necessary power are so dependent upon the 
resistance to be overcome, it is difficult to give definite rules for 
determining them. The following data, based upon actual tests, 



Fig. 149. Belt-Driven Propeller Fan, with Special Type of Blade. 
Courtesy of H ward and Morse, New York City. 


apply to fans working against a resistance such as would be 
produced by connecting with a system of ducts of medium length 
through which the air was drawn at a velocity not greater than 600 
or 800 feet per minute. Under these conditions, a good type of fan 
will propel the air in a direction parallel to the shaft a distance equal to 
about .7 of its diameter at each revolution; and from this we have 
the equation: 
























174 


HEATING AND VENTILATION 


Q = .7 Dx RX A, 

in which 

Q = Cubic feet of air discharged per minute; 
D = Diameter of fan, in feet; 

R = Revolutions per minute; 

A = Area of fan, in square feet. 


In order to obtain the 
best results, the linear velocity 
of air-flow through the fan 
should range from 800 to 1,200 
feet per minute. 

Table XXXVI gives the 
revolutions per minute for 
fans of different diameter to 
produce a linear velocity of 
1,000 feet, the volume deliv¬ 
ered at this speed, and the 
horse-power required. 

The horse-power is com¬ 
puted by allowing .14 H. P. 
for each 1,000 cubic feet of 
air moved, when the velocity 
through the fan is 800 feet 
per minute; .16 H. P. for 



1,000 feet velocity; and .18 H. P. for 1,200 feet velocity. These 
factors are empirical, and based on tests. 



Fig. 151. Fan Belt-Connected to Motor. 

Example. Assuming a velocity of 800 feet per minute through a 4-foot 
fan, what volume will be delivered per minute, and what speed and horse¬ 
power will be required? 




























































HEATING AND VENTILATION 


175 


TABLE XXXVI 


Disc Fans, their Capacity, Speed, etc. 


Dia. of Fan, in 
Inches 

Rev. per Min. 

Cubic Feet of Air 
Moved 

Horse-Power 

Required 

18 

952 

1,700 

.27 

24 

716 

3,100 

.50 

30 

572 

4,900 

.78 

36 

476 

7,100 

1.2 

42 

408 

9,400 

1.5 

48 

343 

12,000 

1.9 

54 

317 

15,800 

2.5 

60 

286 

19,400 

3.1 

72 

238 

28,300 

4.5 


The area of a 4-foot fan is 12.5 square feet; and at 800 velocity 
the volume would be 12.. 5 X 800 = 10,000 cubic feet. Next solve 
for the speed by the equation Q = .7D X R X A, which, when 
transposed, takes the form 

jt _ Q . 

“ .7 DX A 


Substituting the known quantities, we have 

10,000 


R = 


= 28(i 


.7 X 4 X 12.5 
The horse-power is 10 X -14 = 1.4. 

Fan Engines. A simple, quiet-running engine is desirable 
for use in connection with a fan or blower. The engine may be either 
horizontal or vertical; and for schoolhouse and similar work, should 
be provided with a large cylinder, so that the required power may 
be developed without carrying a boiler pressure much above 30 
pounds. In some cases, cylinders of such size are used that a boiler 
pressure of 12 or 15 pounds is sufficient. The quantity of steam 
which an engine consumes is of minor importance, as the exhaust can 
be turned into the coils and used for heating purposes. If space 
allows, the engine should always be belted to the fan. Where it is 
direct-connected, as in Fig. 144, there is likely to be trouble from 
noise, as any slight looseness or pounding in the engine will be com¬ 
municated to the air-ducts, and the sound will be carried to the rooms 















































176 


HEATING AND VENTILATION 


above. Figs. 152 and 153 show common forms of fan engines. The 
latter is especially adapted to this purpose, as all bearings are enclosed 



1 i 

Fig. 152. Vertical Self-Oiling Fan Engine. 

Courtesy of the American Blower Company, Detroit, Michigan. 

and protected from dust and grit. A horizontal engine for fan use 
is shown in Fig. 154. 

In case an engine is belted, the distance between the shafts of 
the fan and engine should not in general be much less than 10 feet 



HEATING AND VENTILATION 


177 


for funs up to 7 or 8 feet in diameter, and 12 feet for those of larger 
size. When possible, the tight or driving side of the belt should 
be at the bottom, so that the loose side, coming on top, will tend to 
wrap around the pulleys and so increase the arc of contact. 

Motors. Electric motors are especially adapted for use in 
connection with fans. This method of driving is more expensive 



Fig 153. Another Form of Fan Engine, with Hearings Enclosed to Protect Them 

from Dust and Grit. 

than by the use of an engine, especially if electricity must be pur¬ 
chased from outside parties; but if the building contains its own 
power plant, so that the exhaust steam can be utilized for heating, 
the convenience and simplicity of motor-driven fans often more than 
offset the additional cost of operation. 

















178 


HEATING AND VENTILATION 


Direct-connected motors are always preferable to belted, if a 
direct current is available, on account of greater quietness of action. 
This is due both to the slower speed of the motor and to the absence 
of belts. 

Sufficient speed regulation can be obtained with direct-connected 
machines, without excessive waste of energy, by putting a rheostat 
in the motor circuit. 

If a direct current is not available and an alternating current 
must be used, the advantages of electric driving are somewhat 
reduced, as high-speed motors with belts or other reducing gear must 
be employed, and, furthermore, satisfactory speed regulation is not 
easily attainable. 



Fig. 154. Horizontal Engine for Fan Use. 

Courtesy of Buffalo Forge Company, Buffalo, New York. 

Area of Ducts and Flues. With the blower type of fan, the size 
of the main ducts may be based*on a velocity of 1,200 to 1,500 feet per 
minute; the branches, on a velocity of 1,000 to 1,200 feet per minute, 
and as low as GOO to 800 feet when the pipes are small. Flue veloci¬ 
ties of 500 to 700 feet per minute may be used, although the lower 
velocity is preferable. The size of the inlet register should be such 
that the velocity of the entering air will not exceed about 300 feet per 
minute; while, on the other hand, the velocity between the inlet 
windows and the fan or heater should not exceed about 800 feet per 
minute. 

The air-ducts and flues are usually made of galvanized iron, the 




HEATING AND VENTILATION 


179 



ducts being run at the basement ceiling. No. 20 and No. 22 iron 
is used for the larger sizes, and No. 24 to No. 28 for the smaller. 

Regulating dampers should 
be placed in the branches lead- • 
ing to each flue, for increasing or 
reducing the air-supply to the 
different rooms. Adjustable de- , 

Hectors are often placed at the 
fork of a pipe for the same pur¬ 
pose. One of these is shown in 
Fig. 155. 

Fig. 156 illustrates a com¬ 
mon arrangement of fan and 

heater where the type of heater Fig . 155 Adjustable Deflector Placed at Fork 
shown in Fig. 138 is used; and of pipe to Regulate Air-suppiy. 

Fig. 157 is a self-contained apparatus in which the heater is inclosed 
in a steel casing. 

Factory Heating. The application of forced blast for the 

COLD A/P INLZr W/NOOWS 


warming of factories and 
shops, is shown in Figs. 
158 and 159. The pro¬ 
portional heating surface 
in this case is generally 
expressed in the number 
of cubic feet in the 
building for each linear 
foot of 1-inch steam 
pipe in the heater. On 
this basis, in factory 
practice, with all of the 
air taken from out of 
doors, there are generally 
allowed from 100 to 150 
cubic feet of space per 
foot of pipe, according as 
exhaust or live steam 
is used, live steam in this case indicating steam of about 80 
pounds pressure. If practically all the air is returned from the 



1 D/SCHAPGC 

oucr rport 

BLOM/CP AT CC/L/NG 


Fig. 156. Common Arrangement of Fan with Heater 
of Type Shown iu Fig. 138. 































































180 


HEATING AND VENTILATION 


buildings to the heater, these figures may be raised to about 140 as a 
minimum, and possibly 200 as a maximum, per foot of pipe. The 



heaters in Table XXXI may be changed to linear feet of 1 inch pipe 
by multiplying the numbers in column three (souare feet of surface) 
by three. 




HEATING AND VENTILATION 


181 


EXAMPLES FOR PRACTICE 

i. A machine shop 100 feet long by 50 feet wide and having 3 
stories, each 10 feet high, is to be warmed by forced blast, using 



Fig. 158. Illustrating Application of Forced Blast for Warming a Factory. 

exhaust steam in the heater. The air is to be returned to the heater 
from the building, and the whole amount contained in the building 
is' to pass through the heater every 15 minutes. What size of blower 








































































































182 


HEATING AND VENTILATION 


will be required, and what will be the H. P. of the engine required to 
run it? How many linear feet of 1-inch pipe should the heater con¬ 
tain? 

j 4-foot blower. 

Ans. | 6 H. P. engine. 

[ 1,071 feet of pipe. 



Fig. 159. Centrifugal Blower Producing Forced Blast for Heating a Shop. 

2. Find the size of blower, engine, and heater for a factory 
200 feet long, 60 feet wide, and having 4 stories, each 10 feet high, 
using live steam at 80 pounds pressure in the heater, and changing 
the air every 20 minutes by taking in cold air from out of doors. 

6-foot blower. 

13 H. P. engine. 
3,200 feet of pipe. 


Ans. 


< 



















































































HEATING AND VENTILATION 


183 


In using this method of computation, judgment must be employed, 
which can come only from experience. The figures given are for 
average conditions of construction and exposure. 

Double=Duct System. The varying exposures of the rooms of 
a school or other building similarly occupied, require that more heat 
shall be supplied to some than to others. Rooms that are on the 
south side of the building and exposed to the sun, may perhaps be 
kept perfectly comfortable with a supply of heat that will maintain 
a temperature of only 50 or GO degrees in rooms on the opposite side 
of the building which are exposed to high winds and shut off from the 
warmth of the sun. 



Fig. 160. Hot-Blast Apparatus with Double Duct for Supplying Air at Different Temper¬ 
atures to Different Parts of a Building. 


With a constant and equal air-supply to each room, it is evident 
that the temperature must be directly proportional to the cooling 
surfaces and exposure, and that no building of this character can be 
properly heated and ventilated if the temperature cannot be varied 
without affecting the air-supply. 

There are two methods of overcoming this difficulty: 

The older arrangement consists in heating the air by means of a 
primary coil at or near the fan, to about GO degrees, or to the minimum 
temperature required within the building. From the coil it passes 
to the bases of the various flues, and is there still further heated as 
required, by secondary or supplementary heaters placed at the base of 
each flue. 





184 


HEATING AND VENTILATION 



With the second and more recent method, a single heater is 
employed, and all the air is heated to the maximum required to 
maintain the desired temperature in the most exposed rooms, while 
the temperature of the other rooms is regulated by mixing with the 
hot air a sufficient volume of cold air at the bases of the different flues. 
This result is best accomplished by designing a hot-blast apparatus 

so that the air shall be 
forced, rather than drawn 
through the heater, and 
by providing a by-pass 
through which it may 
be discharged without 
passing across the heated 
pipes. 

The passage for the 
cool air is usually above 
and separate from the 
heater pipes, as shown in 
Fig. 160. Extending 
from the apparatus is a 
double system of ducts, 
usually of galvanized 
iron, suspended from the 
ceiling. At the base of 
each flue is placed a mix¬ 
ing damper, which is 
controlled by a chain 
from the room above, 
and so designed as to 

adnut either a full vol- 

Fig. 161. Mixing Damper for Regulating Temperature , irn „ 1,~+ ' „ f,,ii 

of Air Supplied by Double-Duct System. Ume Ot XlOt air, a 1 1111 

volume of cool or 


tempered air, or to mix them in any desired proportion without 
affecting the resulting total volume delivered to the room, Fig. 166. 

Fig. 162 shows an arrangement of disc fan and heater where the 
air is first drawn through a tempering coil, then a portion of it forced 
through a second heater and into the warm-air pipes, while the 
remainder is by-passed under the heater into the cold-air pipes. 













































































































































































































































186 


HEATING AND VENTILATION 


ELECTRIC HEATING 

Unless electricity is produced at a very low cost, it is not com¬ 
mercially practicable for heating residences or large buildings. The 
electric heater, however, has quite a wide field of application in heating 
small offices, bathrooms, electric cars, etc. It is a convenient method 
of warming rooms on cold mornings in late spring and early fall, 
when furnace or steam heat is not at hand. It has the special advan¬ 
tage of being instantly available, and the amount of heat can be regu¬ 
lated at will. The heaters are perfectly clean, do not vitiate the air, 
and are portable. 

Electric Heat and Energy. The commercial unit for electricity 
is one watt for one hour, and is equal to 3.41 B. T. U. Electricity is 
usually sold on the basis of 1,000 watt-hours (called Kilowatt-hours), 



Fig. 163 . Electric Car-Heater. 


which is equivalent to 3,410 B. T. U. A watt is the product obtained 
by multiplying a current of 1 ampere by an electromotive force of 1 
volt. 

From the above we see that the B. T. U. required per hour for 
warming, divided by 3,410, will give the kilowatt-hours necessary for 
supplying the required amount of heat. 

Construction of Electric Heaters. Heat is obtained from the 
electric current by placing a greater or less resistance in its path. 
Various forms of heaters have been employed. Some of the simplest 
consist merely of coils or loops of iron wire, arranged in parallel rows, 
so that the current can be passed through as many coils as are needed 
to provide the required amount of heat. In other forms, the heating 
material is surrounded with fire-clay, enamel, or asbestos, and in some 
cases the material itself has been such as to give considerable resist¬ 
ance to the current. A form of electric car-heater is shown in Fig. 163 
Forms of radiators are shown in Figs. 164-and 165 


HEATING AND VENTILATION 


187 


Calculation of Electric Heaters. The formula for the calcu¬ 
lation of electric heaters is 


H = P Rtx .24, 

in which 

H = Heat, in calories; 

I = Current, in amperes; 

R = Resistance, in ohms; 
t = Time, in seconds. 

Examples. What resistance must an 
electric heater have, to give off 6,000 B. 
T. U. per hour, with a current of 20 am¬ 
peres ? 



Fig. 164. Electric Radiator. 


We have learned that 1 B. T. U. = 252 calories; so in the 
present case, 6,000 X 252 = 1,512,000 calories must be provided. 
Substituting the known values in the formula, we have 
1,512,000 = 20 2 X R X 3,600 X .24, 

from which 


R = 


1,512,000 


= 4.37 ohms. 


345,600 

A heater having a resistance of 3 ohms is to supply 3,000 B. T. U. per 
hour. What current will be required ? 



Fig. 165. Another Form of Electric Radiator. 


3,000 X 252 = 756,000 calories. Substituting the known values in 
the formula, and solving for I, we have 

756,000 = P X 3 X 3,600 X .24, 

from which 

1 = V 291.6 = 17 + amperes. 

Connections for Electric Heaters. The method of wiring for 
electric heaters is essentially the same as for lights which require the 
same amount of current. A constant electromotive force or voltage 















188 


HEATING AND VENTILATION 


is maintained in the main wire leading to the heaters. A much less 
voltage is carried on the return wire, and the current in passing through 
the heater from the main to the return, drops in voltage or pressure. 
This drop provides the energy which is transformed into heat. 

The principle of electric heating is much the same as that in¬ 
volved in the non-gravity return system of steam heating. In that 
system, the pressure on the main steam pipes is that of the boiler, 
while that on the return is much less, the reduction in pressure occur¬ 
ring in the passage of the steam through the radiators; the water of 
condensation is received into a tank, and returned to the boiler by a 
pump. 

In a system of electric heating, the main wires must be suffi¬ 
ciently large to prevent a sensible reduction in voltage or pressure 
between the generator and the heater, so that the pressure in them 
shall be substantially that in the generator. The pressure or voltage 
in the main return wire is also constant, but very low, and the genera¬ 
tor has an office similar to that of the steam pump in the system just 
described—that is, of raising the pressure of the return current up 
to that in the main. The power supplied to the generator can be 
considered the same as the boiler in the first case. All the current 
which passes from the main to the return must flow through the heater, 
and in so doing its pressure or voltage falls from that of the main 
to that of the return. 

From the generator shown in Fig. 1G6, main and return wires 
are run the same as in a two-pipe system of steam heating, and these 
are proportioned to carry the required current without sensible drop 
or loss of pressure. Between these wires are placed the various 
heaters, which are arranged so that when electric connection is made 
they draw the current from the main and discharge it into the return 
wire. Connections are made and broken by switches, which take the 
place of valves on steam radiators. 

Cost of Electric Heating. The expense of electric heating must 
in every case be great, unless the electricity can be supplied at an 
exceedingly low cost. Estimated on the basis of present practice, 
the average transformation into electricity does not account for more 
than 4 per cent of the energy in the fuel which is burned in the furnace. 
Although under best Conditions 15 per cent has been realized, it 
would not be safe to assume that in ordinary practice more than 5 


HEATING AND VENTILATION 


189 


per cent could be transformed into electrical energy. In heating 
with steam, hot water, or hot air, the average amount utilized will 
probably be about 60 per cent, so that the expense of electrical heating 
is approximately from 12 to 15 times greater than by these methods. 

TEMPERATURE REGULATORS 

The principal systems of automatic temperature control now in 
use, consist of three essential features; First, an air-compressor, 
reservoir, and distributing pipes; second , thermostats, which are 



Fig. 168. General System of Wiring a House for Electric Heating. 

placed in the rooms to be regulated; and third , special diaphragm or 
pneumatic valves at the radiators. 

The air-compressor is usually operated by water-pressure in 
small plants and by steam in larger ones; electricity is used in some 
cases. Fig. 167 shows a form of water compressor. It is similar 
in principle to a direct-acting steam pump, in which water under 
pressure takes the place of steam. A piston in the upper cylinder 
compresses the air, which is stored in a reservoir provided for the 
purpose. When the pressure in the reservoir drops below a certain 



















































190 


HEATING AND VENTILATION 

* 


point, the compressor is started automatically, and continues to 
operate until the pressure is brought up to its working standard. 

A thermostat is simply a mechanism for opening and closing 
one or more small valves, and is actuated by changes in the tempera- 



pig. 167. Air-Compressor Operated by Wa¬ 
ter-Pressure, Automatically Controlled, 
and Operating to Regulate Temperature 
by Cont-olUng Radiator Valves. 



Fig. 168. Thermostat Controlling Valves 
on Radiators, and Operating through Ex¬ 
pansion or Contraction of Metal Strip E. 


ture of the air in which it is placed. Fig. 168 shows a thermostat 
m which the valves are operated by the expansion and contraction 
of the metal strip E. The degree of temperature at which it acts 
may be adjusted by throwing the pointer at the bottom one way or 
the other. Fig. 169 shows the same thermostat with its ornamental 









































HEATING AND VENTILATION 


191 



casing in place. The thermostat shown in Fig. 170 operates on 
a somewhat different principle. It consists of a vessel separated into 
two chambers by a metal diaphragm. 

One of these chambers is partially 
filled with a liquid which will boil 
at a temperature below that desired 
in the room. The vapor of the 
liquid produces considerable pres¬ 
sure at the normal temperature of 
the room, and a slight increase of 
heat crowds the diaphragm over 
and operates the small valves in a 
manner similar to that of the metal 
strip in the case just described. 

The general form of a dia¬ 
phragm valve is shown in Fig. 171. 

These replace the usual hand-valves 
at the radiators. They are similar 
in construction to the ordinary 
globe or angle valve, except that 
the stem slides up and down in¬ 
stead of being threaded and run¬ 
ning in a nut. The top of the stem 
connects with a flat plate, which 
rests against a rubber diaphragm. 

The valve is held open by a spring, 
as shown, and is closed by admit¬ 
ting compressed air to the space 
above the diaphragm. 

In connecting up the system, 
small concealed pipes are carried 
from the air-reservoir to the ther¬ 
mostat, which is placed upon an 

inside wall of the room, and from Fig. m. Thermostat of Fig. i 68 in 
. . . Ornamental Casing. 

there to the diaphragm valve at 

the radiator. When the temperature of the room reaches the maxi¬ 
mum point for which the thermostat is set, its action opens a small 
valve and admits air-pressure to the diaphragm, thus closing off the 
























192 


HEATING AND VENTILATION 


steam from the radiator. When the temperature falls, the thermostat 
acts in the opposite manner, and shuts off the air-pressure from the 
diaphragm valve, at the same time opening a small exhaust which 
allows the air above the diaphragm to escape. The pressure being 
removed, the valve opens and again admits steam to the radiator. 

Diaphragm Motors. Dampers are operated pneumatically in 
a similar manner to steam valves. A diaphragm motor, so called, is 
acted upon bythe air-pressure; and this lifts a lever which is properly 
connected to the damper by means of chains or levers, thus securing 
the desired movement. 

Dampers. When mixing dampers are operated pneumatically, 
a specially designed thermostat for giving a graduated movement 



Fig. 170. Thermostat.Operating through Expansion or Contraction of the Vapor 

of a Volatile Liquid. 

to the damper should be used. By this arrangement the damper 
is held in such a position at all times as to admit the proper proportions 
of hot and cold or tempered air for producing the desired temperature 
in the room with which it is connected. 

Large dampers which are to be operated pneumatically, should 
be made up in sections or louvres. Dampers constmcted in this 
manner are handled much more easily than when made in a single 
piece. 

It often happens, in large plants, that there are valves and 
dampers in places which are not easily reached for hand manipula¬ 
tion. These may be provided with diaphragms and connected with 
the air-pressure system for operation by hand-switches or cocks 


















HEATING AND VENTILATION 


193 


conveniently located at some central point in the basement or boiler 
room. 

Telethermometer. This is a device for indicating on a dial 
at some central point the temperature of various rooms or ducts in 
different parts of a building. A special transmitter is placed in each 
of the rooms and electrically connected with a central switchboard. 
Then, by means of suitable switches, any room may be thrown in 
circuit with the recorder, and the temperature existing in the room 
at that time read from the dial. 



Fig. 171. Exterior View, and Section Showing Interior Mechanism of Diaphragm Valve. 


Humidostat. The kumidostat is a device to be placed in one or 
more rooms of a building for maintaining an even percentage of 
moisture in the air. The apparatus consists of two essential parts— 
the humidostat and the humidifier. The former corresponds to the 
thermostat in a system of temperature control, and operates a pneu¬ 
matic valve or other mechanism connected with the humidifier when 
the percentage of moisture rises above or falls below certain limits. 
The operating medium is compressed air, the same as for tempera¬ 
ture control; and the two devices are usually connected with the same 
pressure system. 















































194 


HEATING AND VENTILATION 


The normal moisture of a room is 70 per cent, and should never 
exceed that. In cold weather it will be necessary to reduce the 
amount of moisture somewhat, owing to the “sweating 5 5 of w'alls and 
windows. 

The method of moistening the air will depend somewhat upon 
circumstances. If the air for ventilation is delivered to the rooms at 
a temperature not exceeding 70 degrees, the humidifier is best placed 
in the main'air-duct. If the air enters at a higher temperature, the 
humidifier must be located in the same room with the humidostat. 

The moistener or humidifier may be of any one of several forms. 
Where steam heating is used, and where the steam is clean and odor¬ 
less and free from oil from engines, a perforated pipe (or pipes) in the 
air-duct is the simplest and best humidifier. The outlets are properly 
adjusted, and then the humidostat shuts off and lets on the steam 
as required. Sometimes a water spray, particularly of warm water, 
may be used in place of steam. When neither steam jet nor water 
spray is advisable, an evaporating pan containing a steam coil may 
be used, the humidostat controlling the steam to the coil, and the 
water-level in the pan being kept constant by means of a ball-cock. 

AIR-FILTERS AND AIR-WASHERS 

In cases where the air for ventilating purposes is likely to contain 
soot or street dust, it is desirable to provide some form of filter for 
purifying it before delivering to the rooms. If the air-quantity is 
small and there is plenty of room between the inlet windows and 
the fan, screens of light cheesecloth may be used for this purpose. 
The cloth should be tacked to light but substantial wooden frames, 
which can be easily removed for frequent cleaning. These screens are 
usually set up in “saw-tooth” fashion in order to give as much sur¬ 
face as possible in the least space. 

Another arrangement, used in case of large volumes of air, 
is to provide a number of light cloth bags of considerable length, 
through which the air is drawn before reaching the heater. These are 
fastened to a Suitable frame or partition for holding them open. The 
great objection to filters of this kind is their obstruction to the passage 
of the air, especially when filled with dust, the frequent intervals at 
which they should be cleaned, and the great amount of filtering sur¬ 
face required. 


HEATING AND VENTILATION 195 



An apparatus which is 
coming quite generally into 
use for this purpose, and 
which does away with the 
g disadvantages noted, above, 
~ is the spray flier or air- 
*5 washer, one form of which 

<t» • 

> is shown in Fig. 172. Air 
£ enters as indicated, and 
•§ first passes through a tem- 
| pering coil to raise it above 
•-5 the freezing. point in win- 
| ter weather; then passes 
Z through the spray-chamber, 
« wdiere the dirt is removed; 
° then through an eliminator 
o for removing the water; 
.2 and then through a second 
| heater on its way to the 
« fan. 

U 

The water is forced 

Jh 

| through the spray-heads 
£ by means of a small cen- 
^ trifugal pump, either belted 
5 to the fan shaft or driven 

U 

1 by an independent motor. 

m 

I HEATING AND 

c n 

l VENTILATION OF 
| VARIOUS CLASSES 
I OF BUILDINGS 

The different methods 
E used in heating and venti¬ 
lation, together with the 
manner of computing the 
various proportions of the 
apparatus, having been 






























































































































196 


HEATING AND VENTILATION 


taken up, the application of these systems to the different classes 
of buildings will now be considered briefly. 

School Buildings. For school buildings of small size, the furnace 
system is simple, convenient, and generally effective. Its use is con¬ 
fined as a general rule to buildings having not more than six or eight 
rooms. For large ones this method must generally give way to some 
form of indirect steam system with one or more boilers, which occupy 
less space, and are more easily cared for than a number of furnaces 
scattered about in different parts of the basement. As in all systems 
that depend on natural circulation, the supply and removal of air is 
considerably affected by changes in the outside temperature and by 
winds. 

The furnaces used are generally built of cast iron, this material 
being durable, and easily made to present large and effective heating 
surfaces. To adapt the larger sizes of house-heating furnaces to 
schools, a much larger space must be provided between the body and 
the casing, to permit a sufficient volume of air to pass to the rooms. 
The free area of the air-passage should be sufficient to allow a velocity 
of about 400 feet per minute. 

The size of furnace is based on the amount of heat lost by radia¬ 
tion and conduction through walls and windows, plus that carried 
away by air passing up the ventilating flues. These quantities may 
be computed by the usual methods for “loss of heat by conduction 
through walls/’ and “heat required for ventilation.” With more 
regular and skilful attendance, it is safe to assume a higher rate of 
combustion in sehoolhouse heaters than in those used for warming 
residences. Allowing a maximum combustion of 6 pounds of coal 
per hour per square foot of grate, and assuming that 8,000 B. T. U. 
per pound are taken up by the air passing over the furnace, we have 
6 X 8,000 = 48,000 B. T. U. furnished per hour per square foot of 
grate. Therefore, if we divide the total B. T. U. required for both 
warming and ventilation by 48,000, it will give us the necessary grate 
surface in square feet. It has been found in practice that a furnace 
with a firepot 32 inches in diameter, and having ample heating surface, 
is capable of heating two 50-pupil rooms in zero weather. The sizes 
of ducts and flues may be determined by rules already given under 
furnace and indirect steam heating. 

The velocity of the warm air within the uptake flues depends 


HEATING AND VENTILATION 


197 


upon their height and the difference in temperature between the 
warm air within the flues and the cold air outside. The action of 
the wind also affects the velocity of air-flow. It has been found by 
experience that flues having sectional areas of about 6 square feet for 
first-floor rooms, 5 square feet for the second floor, and 4^ square feet 
for the third, will be of ample size for standard classrooms seating 
from 40 to 50 pupils in primary and grammar schools. These sizes 
may be used for both furnace and indirect gravity steam heating. 

The vent flues may be made 5 square feet for the first floor, and 
0 square feet for the second and third floors. They may be ar¬ 
ranged in banks, and carried through the roof in the form of large 
chimneys, or may be carried to the attic space and there gathered 
by means of galvanized-iron ducts connecting with roof vents of 
wood or copper construction. 

In order to make the vent flues “draw” sufficiently in mild or 
heavy weather, it is necessary to provide some means for warming 
the air within them to a temperature somewhat above that of the 
rooms with which they connect. This may be done by placing a 
small stove made specially for the purpose, at the base of each flue. 
If this is done, it is necessary to carry the air down and connect with 
the flue just below the stove. 

The cold-air supply duct to each furnace should be made f 
the size of all the warm-air flues if free from bends, or the full 
size if obstructed in any way. 

The inlet and outlet openings from the rooms into the flues, are 
commonly provided with grilles of iron wire having a mesh of 2 to 2\ 
inches. Both flat and square wire are used for this purpose. Mixing 
dampers for regulating the temperature of the rooms should be pro¬ 
vided for each flue. The effectiveness of these dampers will depend 
largely upon their construction; and they should be made tight 
against cold-air leakage, by covering the surfaces or flanges against 
which they close with some form of asbestos felting. Both inlet and 
outlet gratings should be provided with adjustable dampers. One of 
the disadvantages of this system is the delivery of all the heat to the 
room from a single point, and this not always in a position to give the 
best results. The outer walls are thus left unwarmed, except as the 
heat is diffused throughout the room by air-currents. When there is 
considerable glass surface, as in most of our modern schoolrooms, 


193 


HEATING AND VENTILATION 


draughts and currents of cold air are frequently found along the out¬ 
side walls. 

The indirect gravity system of steam heating comes next in cost 
of installation. One important advantage of this system over furnace 
heating comes from the ability to place the heating coils at the base 
of the flues, thus doing away with horizontal runs of air-pipe, which 
are required to some extent in furnace heating. The warm-air 
currents in the flues are less affected by variations in the direction and 
force of the wind where this construction is possible, and this is of 
much importance in exposed locations. 

The method of supplying cold air to the coils or heaters is im¬ 
portant, and should be carefully worked out. The supply should be 
taken from at least two sides of the building, or, if possible, from all 
four sides. When it is taken from four sides, each inlet should be 
made large enough to supply one-half the amount, or, in other words, 
any two should give the total quantity required. It is often possible 
to arrange the flues in groups so that all the heating stacks may be 
placed in two or more cold-air chambers, depending upon the size 
of the building. A cold-air trunk line may be run through the center 
of the basement, connecting with the outside on all four sides, and 
having branches supplying each cold-air chamber. 

Cast-iron pin-radiators are particularly adapted to this class 
of work. 

The School-Pin, having a section about 10 inches in depth and 
rated at 15 square feet of heating surface per section, is used quite 
extensively for this purpose. Stacks containing about 240 square 
feet of surface for southerly rooms, and 260 for those having a north¬ 
erly exposure, have been found ample for ordinary conditions in zerp 
weather. 

A very‘satisfactory arrangement is the use of indirect heaters 
for warming the air needed for ventilation, and the placing of direct 
radiation in the rooms for heating purposes. The general construc¬ 
tion of the indirect stacks and flues may be the same; but the heating 
surface can be reduced, as the air in this case must be raised only to 
70 or 75 degrees in zero weather, the heat to offset that lost fry con¬ 
duction, etc., through walls and windows being provided by the 
direct surface. The mixing dampers may be omitted, and the tem¬ 
perature of the room regulated by opening or closing the steam valves 


HEATING AND VENTILATION 


199 


on the direct coils, which should be done automatically. The direct- 
heating surface, which is best made up of lines of 1^-inch pipe, should 
be placed along the outer walls beneath the windows This supplies 
heat where most needed, and does away with the tendency to draughts. 
In mild weather, during the spring and fall, the indirect heaters may 
prove sufficient for both ventilation and warming. 

Where direct radiation is placed in the rooms, the quantity of 
heat supplied is not affected by varying wind conditions, as is the 
case in indirect heating. Although the air-supply may be reduced 
at times, the heat quantity is not changed. Direct radiation has the 
disadvantage of a more or less unsightly appearance, and architects 
and owners often object to the running of mains or risers through 
the rooms of the building. ' Air-valves should always be provided 
with drip connections carried to a sink or dry well in the basement. 

When circulation coils are used, a good method of drainage is 
to carry separate returns from each coil to the basement, and to place 
the air-valves in the drops just below the basement ceiling. A check- 
valve should be placed below the water-line in each return. 

The gravity system has the fault of not supplying a uniform 
quantity of air under all conditions of outside temperature, the same 
as a furnace, but when properly arranged, may be made to give quite 
satisfactory results. 

The fan or blower system for ventilation, with direct radiation 
in the rooms for warrhing, is considered to be one of the best possible 
arrangements. 

In designing a plant of this kind, the main heating coil should 
be of sufficient size to warm the total air-supply to 70 or 75 degrees 
in the coldest weather, and the direct surface should be proportioned 
for heating the building independently of the indirect system. Auto¬ 
matic temperature regulation should be used in connection with 
systems of this kind, by placing pneumatic valves on the direct radia¬ 
tion. It is customary to carry from 3 to 8 pounds pressure on the 
direct system, and from 8 to 15 pounds on the main coil, depending 
upon the outside temperature. The foot-warmers, vestibule, and 
office heaters should be placed on a separate line of piping, with 
separate returns and trap, so that they can be used independently 
of the rest of the building if desired. Where there is a large assembly 
hall, it should be arranged so that it cap. be both warmed and venti- 


200 


HEATING AND VENTILATION 


lated when the rest of the building is shut off. This can be done by a 
proper arrangement of valves and dampers. 

When different parts of the system are run on different pressures, 
the returns from each should discharge through separate traps into 
a receiver having connection with the atmosphere by means of a vent 
pipe. Fig. 173 shows a common arrangement for the return con¬ 
nections in a combination system of this kind. The different traps 
discharge into the vented receiver as shown; and the water is pumped 
'back to the boiler automatically wiien it rises above a given level in 
the receiver, a pump governor being used to start and stop the pumps 
as required. 

A water-level or seal of suitable height is maintained in the main 
returns, by placing the trap at the required elevation and bringing 
the returns into it near the bottom; a balance pipe is connected with 
the top for equalizing the pressure, the same as in the case of a pump 
governor. Sometimes a fan is used with the heating coils placed at 
the base of the flues, instead of in the rooms. Where this is done 
the radiating surface may be reduced about one-half. This system 
is less expensive to install, but has the disadvantage of removing the 
heating surface from the cold w r alls, where it is most needed. 

With a blower type of fan, the size of the main ducts may be 
based on a velocity of from 1,000 to 1,200 feet per minute, and the 
branches on a velocity of 800 to 1,000 feet per minute. 

The velocity in the vertical flues may be from 600 to 700 feet per 
minute, although the lower velocity is preferable. 

The size of the inlet registers should be such that the velocity 
of the entering air will not exceed 350 to 400 feet per minute. 

When the air is delivered through a register at the high velocities 
mentioned, some means must be provided for diffusing the entering 
current, in order to prevent disagreeable draughts. This is usually 
accomplished by the -use of deflecting blades of galvanized iron, set 
in a vertical position and at varying angles, so that the air is thrown 
towards each side as it issues from the register. The size of the 
vent flues should be about the same as for a gravity system—that is, 
about 6 square feet for a standard classroom, and in the same pro¬ 
portion for smaller rooms. 

Vent-flue heaters are not usually required in connection with a 
fan system, as the force of the fan is sufficient to supply the required 


HEATING AND VENTILATION 










































































































































202 


HEATING AND VENTILATION 


quantity of air at all times without the aspirating effect of the vent 
flues. 

The method of piping, shown in Fig. 173 applies especially to 
buildings of large size. In the case of medium-sized buildings, it 
is often possible to use pin radiation for the main heater, placing the 
same well above the water-line of the boilers and thus returning the 
condensation by gravity, without the use of pumps or traps. When 
this arrangement is used, an engine with a large cylinder should be 
employed, so that the steam pressure will not exceed 15 or 18 pounds, 
and the whole system, including the direct surface, may be run upon 
the same system.* 

This is a very simple arrangement, and is adapted to all build¬ 
ings of small and medium size where the heater can be placed at a 
sufficient height above the boilers.' 

Temperature control is usually secured automatically by placing 
pneumatic valves upon either the direct or supplementary heaters. 
Mixing dampers are sometimes used instead, in the latter case. Every 
fan system should be provided with a thermometer of large size for 
indicating the temperature of the air in the main duct just beyond 
the fan. 

The ventilation of the toilet-rooms of a school building is a 
matter of the greatest importance. The first requirement is that the 
air-movement shall be into these rooms from the corridors instead of 
outward. To obtain this result, it is necessary to produce a slight 
vacuum within, and this cannot well be done if fresh air is forced 
into them. 

One of the most satisfactory arrangements is to provide exhaust 
ventilation only, and to remove the greater part of the air through 
local vents connecting with the fixtures. 

Hospitals. The best system for heating and ventilating a hos¬ 
pital depends upon the character and arrangement of the buildings. 
It is desirable in all cases to do the heating from a central plant, 
rather than to carry fires in the separate buildings, both on account 
of economy and for cleanliness. 

In the case of small cottage hospitals with two or three buildings 
placed close together, indirect hot water affords a desirable system for 
the wards, with direct heat for the other rooms; but where there are 
several buildings, and especially if they are some distance apart, it 


HEATING AND VENTILATION 


203 


becomes necessary to substaute steam unless the water is pumped 
through the mains. For large city buildings, a fan system is always 
desirable. 

If the building is tall compared with its ground area, so that 
the horizontal supply ducts will be comparatively short, the double¬ 
duct system may be used with good results. Where the rooms are 
of good size, and the number of supply flues not great, the use of 
supplementary heaters at the bases of the flues makes a satisfactory 
arrangement. Direct radiation should never be used in the wards 
when it can be avoided, even in connection with an independent air- 
supply, as it offers too great an opportunity for the accumulation of 
dust in places which are difficult to reach. 

It is common io provide from 80 to 100 cubic feet of air per 
minute per patient in ordinary wards, and from 100 to 120 cubic feet 
in contagious wards. 

The usual ward building of a modern cottage-hospital generally 
contains a main ward having from 8 to 12 beds, and a number of 
priyate rooms of one bed each. 

In addition to these, there are a diet kitchen, duty-room, toilet- 
rooms, bathrooms, linen-closets, and lockers. 

For moderately sheltered locations, 30 square feet of indirect 
„ steam radiation has been found sufficient in zero weather for a single 
ward with one exposed wall and a single window, when upon the 
south side of the building. 

For northerly rooms, 40 square feet should be used. In exposed 
locations, the heaters may be made 40 and 50 square feet for north 
and south rooms respectively. The standard pin-radiators rated at 
10 square feet of heating surface per section, are commonly used for 
this purpose. In case hot water is used, the same number of sections 
of the deep-pin pattern rated at 15 square feet each may be employed, 
making a total of 45 and 00 square fret per room. For corner rooms 
having two exposed walls and two windows, the amount of radiation 
should be increased about 50 per cent over that given above. 

The wards are usually furnished with fireplaces which provide 
for the discharge ventilation. In case the fireplaces are omitted, a 
special vent flue, either of brick or of galvanized iron, should be pro¬ 
vided. These should not be less than 8 by 12 inches for single wards, 
and the equivalent for each bed in a large ward. ‘Each flue of this 


204 


HEATING AND VENTILATION 


kind should have a loop of steam pipe for producing a draught. A 
loop of 1-inch pipe, 10 or 12 feet in height, is usually sufficient for 
this purpose. 

Other rooms than wards are usually heated with direct radia¬ 
tors, the sizes of which may be computed in the same manner as for 
dwelling-houses. 

Steam tables for the kitchen, sterilizers, ajid laundry machinery, 
require higher pressures than is necessary for heating. 

In large plants the boilers are usually run at high pressure, and 
the pressure reduced for heating. A good arrangement for small 
plants is to provide sufficient boiler power for warming and ventilating 
purposes, and run at a pressure of 3 to 5 pounds. In addition to 
this, a small high-pressure boiler carrying 70 or 80 pounds should be 
furnished for laundry work and water heating. 

Churches. Churches may be warmed by furnaces, by indirect 
steam,, or by means of a fan. For small buildings the furnace is 
more commonly used. This apparatus is the simplest of all and is 
comparatively inexpensive. Heat may be generated quickly, and 
when the fires are no longer needed, they may be allowed to go out 
without danger of damage to any part of the system from freezing. 

It is not usually necessary that the heating apparatus be large 
enough to warm the entire building at one time to 70 degrees with 
frequent change of air. If the building is thoroughly warmed before 
occupancy, either by rotation or by a slow inward movement of 
outside air, the chapel or Sunday-school room may be shut off until 
near the close of the service in the auditorium, when a portion of the 
warm air may be turned into it. When the service ends, the switch- 
damper is opened wide, and all the air is discharged into the Sunday- 
school room. The position of the warm-air registers will depend 
somewhat upon the construction of the building, but it is well to keep 
them near the outer walls and the colder parts of the room. Large 
inlet registers should be placed in the floor near the entrance doors, 
to stop cold draughts from blowing up the aisles when the doors are 
opened, and also to be used as foot-warmers. 

Ceiling ventilators are generally provided, but should be no 
larger than is necessary to remove the products of combustion from 
the gaslights, etc. If too large, much of the warmest and purest 
air will escape through them. The main vent flues should be placed 


HEATING AND VENTILATION 


205 


in or near the floor and should be connected with a vent shaft leading 
outboard. This flue should be provided with a small stove or flue 
heater made specially for this purpose. In cold weather the natural 
draught will be found sufficient in most cases. 

The same general rules are to be followed' in the case of 
indirect steam as have been described for furnace heating. The 
stacks are placed beneath the registers or flues, and mixing dampers 
provided, if there are large windows, flues should be arranged to 
open in the window-sills, so that a sheet of warm air may be delivered 
in front of the windows, to counteract the effects of cold down-draughts 
from the exposed glass. These flues may usually be made 3 or 4 
inches in depth, and should extend the entire width of the window. 
Small rooms, such as vestibules, library, pastor’s room, etc., are usually 
heated with direct radiators. Rooms which are used during the 
week are often connected with an independent heater so that they 
may be warmed without running the large boilers, as would otherwise 
be necessary. 

When a fan is used, it is desirable, if possible, to deliver the air 
to the auditorium through a large number of small openings. This 
is often done by constructing a shallow box under each pew, rufming 
its entire length, and connecting it with the distributing ducts or a 
plenum space by means of a pipe from below. The air is delivered 
at a low velocity through a long slot, as shown in Fig. 174. 

The warm-air flues in the window-sills should be retained, but 
may be made shallower, and the air forced in at a high velocity. 

If the auditorium has a sloping floor, a plenum space may be 
provided between the upper or raised portion and the main floor. 
Sometimes a shallow basement 3 or 4 feet in height, with a cemented 
floor, and extending under the entire auditorium, is used as an air 
or plenum space. 

If the basement is of good height and used for storage or other 
purposes, it is necessary to carry galvanized-iron ducts at the ceiling 
under the center of each double row of pews, and to connect with 
each pair by means of branch uptakes. The size of these should 
be equal to 3 or 4 square inches for each occupant. 

Another method is to supply the air through a small register in 
the end of each pew. This simplifies the pew construction some* 
what, but otherwise is not so satisfactory as the preceding method. 


206 


HEATING AND VENTILATION 


If the special pew construction is too expensive, or for any other 
reason cannot well be used, and the fan is to be retained, the greater 
part of the air is best introduced through wall registers placed about 
8 feet above the floor, with exhaust openings at or near the floor. 
By this arrangement the air is thrown horizontally toward the center 
of the church, and much of it falls to the breathing level without 
rising to the upper part of the room. 

Halls. The treatment of a large audience hall is similar to that 
of a church, the warming being usually done in one of the three ways 
already described. Where a fan is used, the air is commonly delivered 

through wall registers placed in 
part near the floor, and partly at a 
height of 7 or 8 feet above it. They 
should be made of ample size, 
so that there will be freedom from 
draughts. A part of the vents 
should be placed in the ceiling, 
and the remainder near the floor. 
All ceiling vents, in both halls and 
churches, should be provided with 
dampers having means for hold¬ 
ing them in any desired position. 
If indirect gravity heaters are 
used, it will generally be necessary 
to place heating coils in the vent 
flues for use in mild weather; but 
if the fresh air is supplied by 
me&ns of a fan, there will usually be 
pressure enough in the room to force the air ©ut without the aid of 
other means. When the vent air-w r ays are restricted, or the air is 
impeded in any way, electric ventilating fans are often used. These 
give especially good results in w r armcr weather, when natural venti¬ 
lation is sluggish. The temperature may be regulated either by 
using the double-duct system or by shutting off or turning on a greater 
or less number of sections in the main heater. After an audience 
hall is once warmed and filled with people, very little heat is required 
to keep it comfortable, even in the coldest weather. 

Theaters, In designing heating and ventilating systems for 



Fig. 174. An Approved Method of De 
livering Warm Air to the Audi¬ 
torium of a Church. 




























HEATING AND VENTILATION 


207 


theaters, a wide experience and the greatest care are necessary to 
secure the best results. A theater consists of three parts: the body 
of the house, or auditorium; the stage and dressing-rooms, and the 
foyer, lobbies, corridors, stairways, and offices. Theaters are usually 
located in cities, and surrounded with other buildings on two or more 
sides, thus allowing no direct connection by windows with the ex¬ 
ternal air; for this reason artificial means are necessary for providing 
suitable ventilation, and a forced circulation by means of a fan is the 
only satisfactory means of accomplishing this. It is usually advisable 
to create a slight excess of pressure in the auditorium, in order that 
all openings shall allow for the discharge rather than the inward 
leakage of air. 

The general and most approved method of air-distribution is 
to force it into closed spaces beneath the auditorium and balcony 
floors, and allow it to discharge upward through small openings 
among the seats. One of the best methods is through chair-legs 
of special latticed design, which are placed over suitable openings in 
the floor; in this way the air is delivered to the room in small streams, 
at a low velocity, without draughts or currents. The discharge 
ventilation should be largely through ceiling vents, and this may be 
assisted if necessary by the use of ventilating fans. Vent openings 
should also be provided at the rear of the balconies, either in the wall 
or in the ceiling, and these should be connected with an exhaust fan 
either in the basement or in the attic, as is most convenient. 

The close seating of the occupants produces a large amount of 
animal heat, which usually increases the temperature from 6 to 10 
degrees, or even more; so that, in considering a theater once filled 
and thoroughly warmed, it becomes more of a question of cooling 
than one of warming to produce comfort. 

The dressing-rooms should be provided with a generous supply 
of fresh air, sufficient to change the entire contents once in 10 minutes 
at least,- and should have discharge flues of sufficient size to carry 
away this amount of air at a velocity not exceeding 300 feet per 
minute, unless connected with an exhaust fan, in which case the 
velocity may be doubled. The foyer, corridors, dressing-rooms, 
etc., are generally heated by direct radiators, which may be con¬ 
cealed by ornamental screens if desired. 

Office Buildings. This class of buildings may be satisfactorily 


208 


HEATING AND VENTILATION 


warmed by direct steam, hot water, or, where ventilation is desired, 
by the fan system. Probably direct steam is used more frequently 
than any other system for this purpose. Vacuum systems are well 
adapted to the conditions usually found in'this type of building, 
as most modern office buildings have their own light and power 
plants, and the exhaust steam can thus be utilized for heating pur¬ 
poses. The piping may be either single or double. If the former 
is used, it is better to carry a single main riser to the upper story, and 
run drops to the basement, as by this means the steam and water 
flow in the same direction, and much smaller pipes can be used than 
would be the case if risers were carried from the basement upward. 

Special provision must be made for the expansion of the risers or 
drops in tall buildings. They are usually anchored at the center, 
and allowed to expand in both directions. The connections with the 
radiators must not be so rigid as to cause undue strains or to lift the 
radiators from the floor; 

It is customary, in most cases, to make the connections with 
the end farthest from the riser; this gives a length of horizontal pipe 
which has a certain amount of spring, and will care for any vertical 
movement of the riser that is likely to occur. Forced hot-water 
circulation, is often used in connection with exhaust steam. The 
water is warmed by the steam in large heaters similar to feed-water 
heaters and is circulated through the system by means of centrifugal 
pumps. This has the usual advantage of hot water over steam, 
inasmuch as the temperature of the radiators may be regulated to 
suit the conditions of outside temperature. 

When a fan system is used the arrangement of the air-ways is 
usually somewhat different from any of those yet described. Owing 
to the great height of these buildings, and the large number of small 
rooms which they contain, it is impossible to carry up separate flues 
from the basement. One of the best arrangements is to construct 
false ceilings in the corridor-ways on each floor, thus forming air- 
ducts which may receive their supply through one or more large up¬ 
takes extending from the basement to the top of the building. These 
corfidor air-ways may be tapped over the door of each room, the 
openings being provided with suitable regulating dampers for gauging 
the air-supply to each’. Adjustable deflectors should be placed in 
the main air-shafts for proportioning the quantity to be delivered 


HEATING AND VENTILATION 


200 


to each floor. If both supply and discharge ventilation are to be 
provided, the fresh air may be carried in galvanized-iron ducts within 
the ceiling spaces, and the remainder used for conveying the exhausted 
air to uptakes leading to a discharge fan placed upon the roof of 
the building. In both of these cases, it is assumed that heat is sup¬ 
plied to the rooms by direct radiation, and that the air-supply is for 
ventilation only. 

Apartment Houses. These are warmed by furnaces, direct 
steam, and hot water. Furnaces are more often used in the smaller 
houses, as they are cheaper to install, and require a less skilful at¬ 
tendant to operate them. Steam is probably used more than any 
other system in blocks of larger size. A well-designed single-pipe 
connection, with autcmatic air-valves dripped to the basement, is 
probably the most satisfactory in this class of work. People who 
are more or less unfamiliar with steam systems are apt to overlook 
one of the valves in shutting off or turning on steam; and where only 
one valve is used, the difficulty arising from this is avoided. Where 
pet-cock air-valves are used, they are often left open through careless¬ 
ness; and the automatic valves, unless dripped, are likely to give more 
or less trouble. 

Greenhouses and Conservatories. Buildings of this class are 
heated in some cases by steam and in others by hot water, some florists 
preferring one and some the other. Either system, when properly 
designed and constructed, should give satisfaction, although hot 
water has its usual advantage of a variable temperature. The 
methods of piping are, in a general way, like those already described, 
and the pipes may be located to run underneath the beds of growing 
plants or above, as bottom or top heat is desired. The main is gen¬ 
erally run near the upper part of the greenhouse and to the farthest 
extremity, in one or more branches, with a pitch upward from the 
heater for hot water and with a pitch downward for steam. The 
principal radiating surface is made of parallel lines of 1^ inch or 
large f r pipe, placed under the benches and supplied by the return 
current. Figs. 175, 176, and 177 show a common method of running 
the piping in greenhouse work. Fig. 175 shows a plan and eleva¬ 
tion of the building with its lines of pipes and Figs. 176 and 177 give 
details of the pipe connections-of the outer and inner groups of pipes 
respectively. 


210 


HEATING AND VENTILATION 


Any system of piping which gives free circulation and which is 
adapted to the local conditions, should give satisfactory results. The 
radiating surface may be computed from the rules already given. 
As the average greenhouse is composed almost entirely of glass, we 




Fig. 175. Plan and Elevation Showing One Method of Running Piping In a Greenhouse 

may for purposes of calculation consider it such; and if we divide 
the total exposed surface by 4, we shall get practically the same 
result as if we assumed a heat loss of 85 B. T. U. per square foot of 
surface per hour, and an efficiency of 330 B. T. U. for the heating 







































































HEATING AND VENTILATION 


211 


coils; so that we may say, in general, that the square feet of radiating 
surface required equals the total exposed surface, divided by 4 for 
steam coils, and by 2.5 for hot-water. These results should be in¬ 
creased from 10 to 20 per cent for exposed locations. 

CARE AND MANAGEMENT 

The care of furnaces, hot-water heaters, and steam boilers has 
been discussed in connection with the design of these different systems 
of heating, and need not be repeated. The management of the 
heating and ventilating systems in large school buildings is a matter 
of much importance, especially in those using a fan system. To obtain 
the best results, as much depends upon the skill of the operating 
engineer as upon that of the, designer. 

Beginning in the boiler-room, he should exercise special care 
in the management of his fires, and the instruction given in “Boiler 
Accessories” should be carefully followed; all flues and smoke 
passages should be kept clear and free from accumulations of soot 
and ashes by means of a brush or steam jet. Pumps and engine should 
be kept clean and in perfect adjustment, and extra care should be 
taken when they are in rooms through which the air-supply is drawm, 
or the odor of oil will be carried to the rooms. All steam traps should 
be examined at regular intervals to see that they are in working order; 
and upon any sign of trouble, they should be taken apart and care¬ 
fully cleaned. 

The air-valves on all direct and indirect radiators should be 
inspected often; and upon the failure of any room to heat properly, 
the air-valve should first be looked to as a probable cause of the diffi¬ 
culty. Adjusting dampers should be placed in the base of each flue, 
so that the flow to each room may be regulated independently. In 
starting up a new plant, the system should be put in proper balance 
by a suitable adjustment of these dampers; and, when once adjusted, 
they should be marked, and left in these positions. The temperature 
of the rooms should never be regulated by closing the inlet registers. 
These should never be touched unless the room is to be unused for 
a day or more. 

In designing a fan system, provision should be made for air- 
roiation ; that is, the arrangement should be such that the same 
air may be taken from the building and passed through the fan and 


212 


HEATING AND VENTILATION 































HEATING AND VENTILATION 


213 


heater continuously. This is usually accomplished by closing Che 
main vent flues and the cold-air inlet to the building, then opening the 
class-room doors into the corridor-ways, and drawing the air down 
the stair-wells to the basement and into the space back of the main 
heater through doors provided for this purpose. In warming up a 
building in the morning, this should always be done until about 
fifteen minutes before school opens. The vent flues should then be 
opened, doors into corridors closed, cold-air inlets opened wide, and 
the full volume of fresh air taken from out of doors. 

At night time the dampers in the main vents should be closed, 
to prevent the warm air contained in the building from escaping. 
The fresh air should be delivered to the rooms at a temperature of 
from 70 to 75 degrees; and this temperature must be obtained by 
proper use of the shut-off valves, thus running a greater or less number 
of sections on the main heater. A little experience will show the 
engineer how many sections to carry for different degrees of outside 
temperature. A dial thermometer should be placed in the main 
warm-air duct near the fan, so that the temperature of the air delivered 
to the rooms can be easily noted. 

The exhaust steam from the engine and pumps should be turned 
into the main heater; this will supply a greater number of sections 
in mild weather than in cold, owing to the less rapid con¬ 
densation. 


moEX 


INDEX 


A PAGE 

Air-compressor. 189 

Air distribution. 12 

Air-filters and air-washers. 194 

Air-venting. 105 

Altitude gauge. 104 

Anemometer. 11 

Automatic return pumps. 130 

B 

Balance pipe. 131 

Blow-off tank. 68 

Boiler connections. 67 

Boilers, steam heating, care and management of. 92 

British thermal unit. 13 

C 

Centrifugal fans... 159 

Chimney flues. 28 

Circulation coils. 45 

Cold-air box. 28 

Cold-air ducts. 82 

Combustion chamber. 24 

D 

Damper-regulator. 134 

Dampers.77, 192 

Diaphragm motors. 192 

Diaphragm valve. 191 

Direct hot-water heating.4, 97 

Direct-indirect radiators.4, 91 

Direct steam heating.2, 42 

Disc or propeller fans. 171 

E 

Electric heat and energy. 186 





























2 


INDEX 


Electric heaters page 

calculation of. 1S7 

connections for. 187 

construction of. 186 

Electric heating.6, 186 

cost of. 188 

Exhaust head. 130 

Exhaust-steam heating.5, 124 

Expansion tank. 103 

F 

Fans. 159 

centrifugal. 159 

disc or propeller. 171 

electric motors for. 177 

engines for. 175 

Firepot. 23 

Forced blast. 147 

cast-iron heaters, efficiency of. 157 

double-duct system. 183 

ducts and flues, areas of. 178 

factory heating. 179 

fan engines. 175 

fans. 159 

heating surface, forms of.:. 148 

pipe-heaters, efficiency of. 152 

plenum method. 148 

Forced blast heating. 6 

Forced hot-water circulation. 117 

Furnaces.1, 19 

care and management of. 34 

chimney flues. 28 

cold-air box.'. 28 

combination systems. 33 

combustion chamber.*. 24 

efficiency of. 25 

firepot. 23 

grates.>. 22 

heating capacity. 26 

heating surface.,v.i. 25 

. 27 










































INDEX 


3 


Furnaces (continued) page 

radiator. 24 

registers. 33 

return duct. 29 

smoke pipes. 27 

types of. 20 

warm-air pipes. 30 


G 

Grates. 

Grease extractor. 


22 

127 


Heat loss from buildings. 13 

Heaters. 122 

efficiency of. 74 

types of.•.. 72 

Heating and ventilation.1,213 

air-filters and air-washers.. 194 

care and management of boilers. 92, 116, 211 

direct hot-water heating. 97 

direct steam heating. 42 

electric heating. 186 

exhaust steam heating. 124 

fans. 159 

forced hot-water circulation. 117 

furnace heating. 19 

heat loss from buildings... 13 

hot-water heaters. 94 

indirect hot-water heating. 113 

indirect st am heating. 71 

methods for various classes of buildings. 195 

principles of ventilation. 7 

steam boilers. 36 

systems of warming. 1 

temperature regulators... 189 

vacuum systems. 141 

Heating and ventilation of buildings. 195 

apartment houses. 209 

churches. 204 

greenhouses and conservatories. 209 






































4 


INDEX 


Heating and ventilation of buildings (continued) page 

halls. 206 

hospitals. 202 

office buildings. 207 

school buildings. 196 

theatres. 206 

Heating systems. 1 

direct hot-water. 4 

direct-indirect radiators. 4 

direct steam. 2 

electric heating. 6 

exhaust steam. 5 

forced blast. 6 

furnaces. 1 

indirect hot-water. 5 

indirect steam. 3 

stoves. 1 

Horsepower for ventilation. 42 

Hot-water heaters. 94 

Hot-water heaters, care and management of. 116 

Humidostat. 193 

I 

Indirect heaters, efficiency of. 74 

Indirect hot-water heating..5, 113 

Indirect steam heating.3, 71 


M 


Mains and branches, sizes of. 


118 


Paul vacuum heating system. 145 

Pipe connections.89, 105, 115, 135, 157 

Pipe heaters, efficiency of. 152 

Pipe radiators. 45 

Pipe sizes.. .60, 90, 110, 116, 159 

Pipes, expansion of. 56 

Piping, systems of..49, 101, 117 

Plenum method of forced blast. 148 

Pumps. 120 



































INDEX 


5 


R PAGE 

Radiators.24, 47 , 100 

cast-iron. 43 

connections. 55 

electric. 187 

efficiency of. 47 , 100 

location of. 49 

pipe. 45 

types of. 114 

Registers. 87 

Return-duct.:. 29 

Return traps. 132 

S 

Sectional boilers. 39 

Stacks and casings. 77 

Stacks, size of. 114 

Steam boilers. 36 

sectional. 39 

tubular. 36 

Stoves. 1 


air flow through flues of various heights under varying 


conditions of temperature. 86 

air, number of changes in, required in various rooms. 11 

air, power required for moving under different condi¬ 
tions.•. 170 

air, quantity of, required per person. 10 

air required for ventilation of various classes of buildings. 10 

boiler, size of, for different conditions. 38 

direct radiating surface supplied by mains of different 

sizes and lengths of run. Ill 

disc fans, capacity, speed, etc. 175 

fan speeds, pressures, and velocities of air-flow. 165 

fans, effective area of. 167 

firepot dimensions. 27 

flow of steam in pipes of other lengths than 100 ft., 

factors for calculating. 62 

flow of steam in pipes of various sizes. 61 
































INDEX 


6 • 

Tables (continued) page 

flow of steam in pipes under initial pressure above 5 lb., 

factors for calculating. 61 

grate area per H. P. for different rates of evaporation and 

combustion. 37 

heat loss, factors for calculating for other than southern 

exposure.... 15 

heat losses in B.T.U. per sq. ft. of surface per hour, 

southern exposure. 14 

heaters, dimensions of. 155 

heating surface supplied by pipes of various sizes. 64 

heating systems, relative cost of. 4 

indirect radiating surface supplied for pipes of various 

sizes. 91 

mains, sizes of, for different conditions. 121 

oval pipe dimensions. 32 

pipe heater data. 154 

pipe sizes.>. 159 

pipe sizes for radiator connections....... 66 

pipe sizes from boiler to main header. 67 

radiating surface on different floors supplied by pipes 

of different sizes..•. Ill 

radiating surface supplied by pipes of various sizes, 

indirect hot-water system. 116 

radiating surface supplied by steam risers.. 65 

radiators, coils, etc., efficiency of. 47 

registers, sizes of for different sizes of pipe.>. 33 

return, blow-off, and feed pipes, sizes of. 68 

steam pipes, sizes of returns for. 66 

warm-air pipe dimensions. 30 

T elethermometer. 193 

Temperature regulators. 189 

air-compressor. 189 

damper. 192 

diaphragm motor.:. 192 

diaphragm valve. 191 

humidostat. . . . 193 

telethermometer. 193 

Thermostat. 190 

Tubular boilers. 36 

/ 


































INDEX 


7 


V PAGE 

V acuum system of heating. 141 

Paul system. 145 

Webster system. 141 

Valves.58, 109 

air valves.58, 109 

angle, offset, and corner. 58 

back-pressure. 128 

fittings. 109 

globe. 58 

reducing. 120 

vacuum. 60 

Vent flues. 83 

Ventilation, principles of. 7 

air distribution. 12 

air required for ventilation. 9 

composition of atmosphere.:. 7 

analysis of air. 8 

carbonic acid gas. 7 

nitrogen. 7 

oxygen. 7 

force for moving air. 11 

measurements of velocity. 11 

W 

Warm-air flues. 81 

Warm-air pipes. 30 

Water-seal motor. 143 

Water-tube boilers. 39 

Webster vacuum heating system. 141 









































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